Method of manufacturing developer container, developer container, developing apparatus, process cartridge, and image forming apparatus

ABSTRACT

A method of manufacturing a developer container including a frame configured to define a developer containing portion, a first electrode, and a second electrode arranged on a surface of the frame and having a surface opposed to the first electrode, a developer amount in the developer containing portion being detected based on a capacitance between the first electrode and the second electrode, the method including: holding a conductive resin member constituting the second electrode on a mold configured to mold the frame, a surface of the conductive resin member being in contact with a surface of the mold configured to mold a surface of the frame on a side of the developer containing portion; injecting a resin to be formed into the frame, into the mold on which the conductive resin member is held; and curing the resin to form the frame to which the second electrode is fixed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 14/958,478, filed Dec. 3, 2015, which is a divisionalapplication of U.S. patent application Ser. No. 14/322,091, filed Jul.2, 2014, now U.S. Pat. No. 9,250,567, which claims the benefit ofJapanese Patent Application No. 2013-146567, filed Jul. 12, 2013,Japanese Patent Application No. 2013-197570, filed Sep. 24, 2013,Japanese Patent Application No. 2013-197563, filed Sep. 24, 2013,Japanese Patent Application No. 2014-113492, filed May 30, 2014,Japanese Patent Application No. 2013-146569, filed Jul. 12, 2013, andJapanese Patent Application No. 2014-125611, filed Jun. 18, 2014. All ofthese prior applications are incorporated by reference herein in theirentirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method of manufacturing a developercontainer to be used in an image forming apparatus such as a copyingmachine, a printer, and a facsimile machine of an electrophotographicprinting method or an electrostatic recording process, and to adeveloper container, a developing apparatus, a process cartridge, and animage forming apparatus.

Description of the Related Art

Electrophotographic image forming apparatus, for example, are hithertoprovided with a developing apparatus configured to form a developerimage by supplying a developer to an electrostatic latent image formedon an electrophotographic photosensitive member (photosensitive member)as an image bearing member. In recent years, developing cartridges orprocess cartridges are widely used which include the developingapparatus alone or along with other process means and which aredetachably mountable to the main body of the image forming apparatus.

A cartridge method in which a developing cartridge or a processcartridge (The developing cartridge or the process cartridge mayhereinafter simply be referred to as “cartridge”.) is detachablymountable to the main body of an image forming apparatus facilitates thesupplying of the developer and other types of maintenance work.

For the cartridge method, in general, an operator such as a user or aservice person replaces the cartridge or supplies the developer at thetime the developer in a developer container of the developing apparatusis used up, thereby enabling the image forming apparatus to form imagesagain. It is therefore common for an image forming apparatus of thecartridge method to have detecting means for detecting the amount(remaining amount) of the developer in order to detect the consumptionof the developer and inform the user or others of when to replace thecartridge.

A type of the detecting means is one that uses a capacitance detectionmethod in which, as disclosed in Japanese Patent Application Laid-OpenNo. 2001-117346, the developer amount is detected by providing a pair ofan input-side electrode and an output-side electrode to measure thecapacitance between the electrodes. The electrodes are in generalantenna members which are made of metal and shaped into a plate (SUSsheet metal or the like).

Japanese Patent Application Laid-Open No. 2003-248371 discloses anotherexample in which a developer carrying member in a developing apparatusthat applies an AC voltage to the developer carrying member serves asthe input-side electrode and a capacitance detecting member serving asthe output-side electrode is arranged in the developing apparatus so asto face the developer carrying member. This capacitance detecting memberalso is in general an antenna member which is made of metal and shapedinto a plate (SUS sheet metal or the like).

The capacitance between the electrodes (between the antenna members, orbetween the developer carrying member and the antenna member) in thecapacitance detection method varies depending on the amount of thedeveloper which is constituted of an insulating toner and others.Specifically, the capacitance between the electrodes is large when thespace between the electrodes is filled with the developer, and decreasesas the developer dwindles and air takes up the space between theelectrodes at an increasing ratio. Accordingly, the developer amount canbe detected by obtaining the relation of the developer amount to thecapacitance between the electrodes in advance and measuring thecapacitance.

However, using the electrode plates described above, such as SUS sheetmetal, for the antenna members tends to increase the cost of partsrelatively. Consequently, increasing the antenna members in size ornumber in order to, for example, improve the precision of developeramount detection or accomplish successive detection of the remainingdeveloper amount from an earlier stage at the start of use is likely toincrease the cost of the developer container and other components.

Japanese Patent Application Laid-Open No. 2002-40906 discloses, as amethod of fixing the antenna members, a method that uses a double-sidedadhesive tape to stick the antenna members to a frame that forms adeveloper container of a developing apparatus. Japanese PatentApplication Laid-Open No. 2002-40906 also discloses that, as analternative, a conductive paint layer or vapor deposition layer may beformed directly on the frame by performing printing or evaporationdirectly on the frame, or a conductive portion may be formed by thetwo-color molding of conductive resin, but does not disclose a detaileddescription of the alternative.

Japanese Patent Application Laid-Open No. H08-15975 discloses a methodof forming an electrode layer by applying a coating solution in which anappropriate amount of fine carbon black particles is dispersed in ablend solution of a urethane resin and a vinyl chloride resin to a sheetbase and thermally curing the applied coat.

However, the methods described above which involve sticking the antennamembers to the frame with double-sided adhesive tape or forming theantenna members on the frame by evaporation or printing tend tocomplicate the manufacturing steps for reasons including the need for astep of processing the frame after the forming of the frame.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above, and thepresent invention therefore provides a method of manufacturing easily adeveloper container whose developer amount is detected by thecapacitance detection method.

The present invention provides a developer container, a developingapparatus, and a process cartridge which improves the precision ofdeveloper amount detection by the capacitance detection method whenconductive resin members are used for electrodes.

In view of the above, according to an embodiment of the presentinvention, there is provided a method of manufacturing a developercontainer including a frame configured to define a developer containingportion, a first electrode, a second electrode which is arranged on asurface of the frame and which has a surface opposed to the firstelectrode, a developer amount in the developer containing portion beingdetected based on a capacitance between the first electrode and thesecond electrode, the method comprising: holding a conductive resinmember constituting the second electrode on a mold configured to moldthe frame, a surface of the conductive resin member being in contactwith a surface of the mold, the surface of the mold being configured tomold a surface of the frame on a side of the developer containingportion; injecting a resin to be formed into the frame, into the mold onwhich the conductive resin member is held; and curing the resin to formthe frame to which the second electrode constituted by the conductiveresin member is fixed.

Further, according to another embodiment of the present invention, thereis provided a developer container configured to contain a developer, thedeveloper container comprising an antenna member configured to detect adeveloper amount by use of a capacitance, wherein the antenna membercomprises a conductive resin member having a resistance of 10³Ω or moreand 10⁵Ω or less.

Further, according to still another embodiment of the present invention,there is provided a developer container, comprising: a frame configuredto define a developer containing portion; a first electrode; and asecond electrode which is arranged on a surface of the frame and whichhas a surface opposed to the first electrode, wherein a developer amountin the developer containing portion is detected based on a capacitancebetween the first electrode and the second electrode, the secondelectrode is constituted by a conductive resin member, a closest point,in which the second electrode is closest to the first electrode, on thesecond electrode is located in a position other than an end portion ofthe second electrode as viewed along an axial direction of the firstelectrode, the second electrode has at least one convex portionprotruding toward the first electrode, and the closest point is locatedon the at least one convex portion.

Further, according to yet still another embodiment of the presentinvention, there are provided a developing apparatus, a processcartridge, and an image forming apparatus including the above-mentioneddeveloper container.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of an image forming apparatusaccording to a first embodiment.

FIG. 2 is a schematic sectional view of a process cartridge according tothe first embodiment.

FIG. 3 is a schematic sectional view of a developing apparatus accordingto the first embodiment.

FIG. 4 is a graph showing a relation between the toner amount and thecapacitance in the first embodiment.

FIGS. 5A, 5B, 5C, and 5D are schematic views illustrating steps ofmanufacturing a developing frame according to the first embodiment.

FIGS. 6A and 6B are sectional views of a part of the developing frame inthe vicinity of an antenna member according to the first embodiment.

FIGS. 7A, 7B, and 7C are sectional views of parts of the developingframes in the vicinity of antenna members according to ComparativeExamples 1 and 2.

FIG. 8 is a schematic sectional view of a developing apparatus ofExample 2 according to the first embodiment.

FIG. 9 is a schematic sectional view of a developing apparatusillustrating the schematic configuration of a detecting device accordingto a second embodiment as well.

FIG. 10 is a graph showing a relation between the remaining toner amountand the capacitance in the second embodiment.

FIGS. 11A and 11B are graphs respectively showing relations between theremaining toner amount and the capacitance in Example 3 according to thesecond embodiment and Comparative Example 3.

FIGS. 12A, 12B, and 12C are schematic views each illustrating an exampleof a conductive resin sheet.

FIG. 13 is a schematic diagram of a toner remaining amount detectingcircuit.

FIGS. 14A and 14B are respectively a plan view of an example of anantenna member and an explanatory diagram of a resistance measuringmethod.

FIGS. 15A and 15B are perspective views illustrating the arrangement ofthe antenna member in a developing frame.

FIG. 16 is a schematic sectional view of a developing apparatusaccording to a third embodiment.

FIG. 17 is a flowchart of processing in which the remaining toner amountis detected and indicated.

FIG. 18 is a schematic sectional view of a mold illustrating steps ofmanufacturing a developer container according to the third embodiment.

FIG. 19 is a graph showing an example of a relation between theremaining toner amount and the capacitance in the third embodiment.

FIGS. 20A and 20B are schematic views illustrating the way of tonerdeposition in the developer container.

FIG. 21A is a schematic sectional view of a substantial part of thedeveloping apparatus according to the third embodiment.

FIG. 21B is a graph illustrating a relation between transitions of thecapacitance detection result and the position of an antenna member.

FIG. 22A is a schematic sectional view of a substantial part of adeveloping apparatus according to Comparative Example 5.

FIG. 22B is a graph illustrating a relation between transitions of thecapacitance detection result and the position of the antenna member.

FIG. 23A is a schematic sectional view of a substantial part of adeveloping apparatus according to a fourth embodiment.

FIG. 23B is a graph illustrating a relation between transitions of thecapacitance detection result and the position of an antenna member inthe fourth embodiment.

FIG. 24A is a schematic sectional view of a substantial part of adeveloping apparatus according to a fifth embodiment.

FIG. 24B is a graph showing an example of a relation between theremaining toner amount and the capacitance.

FIG. 24C is a graph illustrating a relation between transitions of thecapacitance detection result and the position of an antenna member.

FIG. 25A is a schematic sectional view of a substantial part of adeveloping apparatus according to Comparative Example 6.

FIG. 25B is a graph illustrating a relation between transitions of thecapacitance detection result and the position of an antenna member.

DESCRIPTION OF THE EMBODIMENTS

A developer container manufacturing method, a developer container, adeveloping apparatus, a process cartridge, and an image formingapparatus according to the present invention will be described in moredetail below with reference to the drawings.

First Embodiment I. Overall Configuration and Operation of an ImageForming Apparatus

FIG. 1 is a schematic sectional view of an image forming apparatusaccording to a first embodiment of the present invention. The imageforming apparatus of the embodiment which is denoted by 100 is a laserbeam printer configured to form an image by the electrophotographicprinting method. The image forming apparatus 100 employs the cartridgemethod, and includes a process cartridge 120 which is detachablymountable to an apparatus main body 110.

An external host device such as a personal computer or an image readingdevice is connected to the image forming apparatus 100. The imageforming apparatus 100 receives image information from the host device,forms an image according to the image information on a recordingmaterial (a recording medium or a transfer material), and outputs(prints) the image. A sheet material such as paper is preferred as therecording material.

The image forming apparatus 100 has, as an image bearing member, aphotosensitive drum 1 which is a drum-shaped (cylindrical)electrophotographic photosensitive member (photosensitive member). Thefollowing means are arranged around the photosensitive drum 1 in orderalong the rotation direction of the photosensitive drum 1. First, acharging roller 2 which is a roller-shaped charging member is arrangedto serve as charging means. Next, an exposure device (laser scannerunit) 3 is arranged to serve as exposure means. A developing apparatus 4which serves as developing means follows next. A transfer roller 5 whichis a roller-shaped transfer member is arranged next to serve as transfermeans. A cleaning device 6 which serves as cleaning means follows next.

When a print start signal is input to the image forming apparatus 100and image formation is started, a rotational driving force istransmitted to the photosensitive drum 1 from a drive motor (not shown)which is provided in the apparatus main body 110 to serve as drivingmeans. The photosensitive drum 1 is thus driven to rotate in a directionindicated by an arrow X1 of FIG. 1 at a predetermined peripheralvelocity (process speed), for example, 147.6 mm/s. The photosensitivedrum 1 in the embodiment includes a drum base made of aluminum and anOPC photosensitive layer provided on the drum base. The charging roller2 is arranged so as to be in contact with the photosensitive drum 1, androtates in association with the rotation of the photosensitive drum 1. Asurface (circumferential surface) of the rotating photosensitive drum 1is charged by the charging roller 2 substantially uniformly to apredetermined electric potential of a predetermined polarity (thenegative polarity in the embodiment). During the charging, apredetermined charging bias (charging voltage) is applied to thecharging roller 2 from a charging power source (high-voltage powersource) (not shown) which is provided in the apparatus main body 110. Inthe embodiment, an oscillation voltage created by superimposing an ACvoltage Vpp of 1.6 kV (frequency: 1,600 Hz), which causes the chargingroller 2 to discharge sufficiently, on a DC voltage Vdc of −560 V, whichcorresponds to a dark section potential Vd on the photosensitive drum 1,is applied as the charging bias. The AC component of the charging biasis controlled by constant-current control so that a substantiallyconstant current flows between the photosensitive drum 1 and thecharging roller 2.

The charged surface of the photosensitive drum 1 is exposed to laserlight L which is emitted from the exposure device 3 in accordance withthe image information. The exposure device 3 outputs, from a laseroutput portion 3 a, the laser light (exposure light) L modulatedaccording to time-series electric digital image signals of the imageinformation, which is input from a personal computer 20 or the like to avideo controller 19. The laser light L output from the exposure device 3enters the interior of the process cartridge 120 and irradiates thesurface of the photosensitive drum 1. The substantially uniformlycharged surface of the photosensitive drum 1 is scanned with and exposedto the laser light L, with the result that an electrostatic latent image(electrostatic image) according to the image information is formed onthe surface of the photosensitive drum 1. In the embodiment, a brightsection potential V1 on the photosensitive drum 1 irradiated with thelaser light L is −130 V. An image part of the electrostatic latent imageis exposed (an image exposure method) in the embodiment.

The electrostatic latent image formed on the surface of thephotosensitive drum 1 is developed by the developing apparatus 4 withthe use of a toner T as a developer. Details of the developing apparatus4 will be described later.

Meanwhile, a pickup roller 8 as conveying means is driven atpredetermined control timing to feed sheets of recording material P suchas recording paper stacked on a recording material tray 7, which servesas a recording material containing portion, one sheet at a time. Therecording material P is thus conveyed to a transfer portion N byconveying means (not shown) at the predetermined control timing. Thetransfer roller 5 is brought into contact with the surface of thephotosensitive drum 1 at a predetermined pressing force to form thetransfer portion (transfer nip) N. The recording material P is conveyedto the transfer portion N via a transfer guide 9, which serves as aguide member. While the recording material P nipped by thephotosensitive drum 1 and the transfer roller 5 is being conveyedthrough the transfer portion N, the toner image on the surface of thephotosensitive drum 1 is transferred electrostatically to a surface ofthe recording material P. At this point, a transfer bias (transfervoltage) which is a DC voltage having a polarity opposite to the tonercharging polarity (the negative polarity in the embodiment) fordeveloping is applied to the transfer roller 5 from a transfer powersource (high voltage power source) (not shown) provided in the apparatusmain body 110.

The recording material P on which the toner image has been transferredis separated from the photosensitive drum 1 and conveyed to a fixingdevice 10, which is provided downstream of the transfer portion N in thedirection of conveyance of the recording material P and which serves asfixing means. The recording material P receives toner image fixingprocessing in the fixing device 10 through heating and pressurizing. Thefixing device 10 in the embodiment includes a heating roller whichcontains a halogen heater inside and a pressure roller which is pressedagainst the heating roller. The fixing device 10 heats and pressurizesthe toner image transferred onto the surface of the recording material Pwhile the recording material P is being held and conveyed between theheating roller and the pressure roller which form a fixing nip. Thetoner image is thus fused and fixed on the surface of the recordingmaterial P. The recording material P is then discharged onto a dischargetray 11, which is provided on an upper part of the apparatus main body110 in FIG. 1.

The surface of the photosensitive drum 1 after the recording material Pis separated is cleaned by the cleaning device 6 to be subjectedrepeatedly to the image forming process described above which startswith the charging. The cleaning device 6 uses a cleaning blade 61, whichis a cleaning member arranged so as to abut against the photosensitivedrum 1, to remove extraneous matter such as a residual toner remainingafter transfer from the surface of the rotating photosensitive drum 1,and collects the extraneous matter in a collected toner container 62.

II. Process Cartridge

FIG. 2 is a schematic sectional view of the process cartridge 120. Inthe embodiment, the photosensitive drum 1 and the process means foracting on the photosensitive drum 1, namely, the charging roller 2, thedeveloping apparatus 4, and the cleaning device 6, are integrally madeinto a cartridge to form the process cartridge 120 which is detachablymountable to the apparatus main body 110.

The process cartridge 120 is constructed by coupling a cleaning unit 12and a developing unit (developing apparatus) 4 which is a separate unitfrom the cleaning unit 12.

The cleaning unit 12 includes the photosensitive drum 1, the chargingroller 2, and the cleaning device 6. The cleaning unit 12 also has acleaning frame 60 which forms the collected toner container 62 andsupports the photosensitive drum 1, the charging roller 2, and thecleaning blade 61. Details of the developing unit 4 will be describedlater.

Process cartridges in general are defined as a cartridge whichintegrally includes an image bearing member such as a photosensitivemember and process means for acting on the image bearing member, andwhich is detachably mountable to the apparatus main body of an imageforming apparatus. The process means include, for example, chargingmeans, developing means, cleaning means, and toner charging means forcharging a residual toner remaining after transfer. The processcartridge here is a cartridge which integrally includes at least adeveloper container or a developing apparatus and an image bearingmember, and which is detachably mountable to the apparatus main body ofan image forming apparatus.

III. Developing Apparatus

FIG. 3 is a schematic sectional view of the developing apparatus 4 inthe embodiment. FIG. 3 also schematically illustrates function blockswhich constitute a detecting device 130, which will be described later.

The developing apparatus 4 of the embodiment has a developing frame 40which forms a developer container 46 configured to contain a magneticsingle-component developer (toner) T as a developer, and which supportscomponents described later. The developer container 46 includes adeveloping chamber 46 a and a toner chamber 46 b. In the embodiment, thedeveloping chamber 46 a and the toner chamber 46 b which are formed fromthe developing frame 40 and which can contain the toner T constitute adeveloper containing portion 40 a.

A developing sleeve 41 is arranged in the developing chamber 46 a so asto be partially exposed to the outside of the developing chamber 46 afrom an opening 46 c, which is formed in the developing chamber 46 a onthe side of the photosensitive drum 1. The developing sleeve 41 is acylindrical member formed from a nonmagnetic material as a developercarrying member. The developing sleeve 41 is supported by the developingframe 40 in a manner that allows the developing sleeve 41 to rotate. Thedeveloping sleeve 41 faces the photosensitive drum 1 across apredetermined gap. A rotational driving force is transmitted to thedeveloping sleeve 41 from the drive motor (not shown) which is providedin the apparatus main body 110 to drive and rotate the developing sleeve41 in a direction indicated by an arrow X2 of FIG. 3. A magnet roller 44which has a plurality of magnetic poles in the circumferential directionis arranged in the hollow portion of the developing sleeve 41 to serveas magnetic field generating means. The magnet roller 44 is supported bythe developing frame 40 in a fixed manner (irrotationally). A developingblade 42 which is a regulating member formed from an elastic material toserve as developer layer regulating means is arranged in the developingchamber 46 a so as to abut against the circumferential surface of thedeveloping sleeve 41. The developing blade 42 is supported by thedeveloping frame 40.

In the toner chamber 46 b, an agitating member 45 is arranged asdeveloper agitating means. The agitating member 45 includes a supportrod 45 a and an agitating sheet 45 b which is fixed to the support rod45 a. The support rod 45 a is supported by the developing frame 40 in amanner that allows the support rod 45 a to rotate. A rotational drivingforce is transmitted to the agitating member 45 from the drive motor(not shown) which is provided in the apparatus main body 110 to driveand rotate the agitating member 45 in a direction indicated by an arrowX3 of FIG. 3. With the rotational driving of the agitating member 45,the toner T contained in the toner chamber 46 b is conveyed from thetoner chamber 46 b to the developing chamber 46 a through a toner supplyopening 46 d, which is an opening for communication between thedeveloping chamber 46 a and the toner chamber 46 b.

The toner supply opening 46 d is closed (sealed) by a sealing member 48(see FIG. 16) in order to prevent toner leakage during the shipping ofthe process cartridge 120. The sealing member 48 is present for tonerleakage prevention until the process cartridge 120 starts to be used.The sealing member 48 may be removed manually or may be removedautomatically by providing a seal breaking member in the toner chamber46 b or the developing chamber 46 a and driving the seal breaking memberso that the sealing member 48 is rolled up and out of the way, orotherwise removed. The seal breaking member may double as an agitatingmember. For instance, in the case of an agitating member that includesan agitating shaft and an agitating sheet member, the agitating sheetmember may double as a toner sealing member while the agitating shaft isgiven the function of the seal breaking member. Alternatively, a tonersealing member may be attached to the agitating shaft separately fromthe agitating sheet member (FIG. 16). As for the electrodes configuredto detect the developer amount, if the sealing member rotates andagitates while holding in the developer, a certain level of capacitanceis detected between the electrodes despite the fact that there is nodeveloper that can be used to form an image. This may be prevented byopening a hole in other parts of the toner sealing member than the tonersealing portion so that the developer caught in the rotating tonersealing member drops down to the bottom of the container. The toner T iscontained only in the toner chamber 46 b out of the developing chamber46 a and the toner chamber 46 b until the sealing member 48 is removed(FIG. 3).

An antenna member 43 which constitutes the detecting device 130described later is arranged on a part of the bottom of the toner chamber46 b.

The toner T conveyed to the developing chamber 46 a is attracted to thedeveloping sleeve 41 by the magnetic force of the magnet roller 44contained in the developing sleeve 41, and is conveyed by the rotationof the developing sleeve 41 to the abutment portion where the developingblade 42 and the developing sleeve 41 abut against each other (FIG. 3).By passing through the abutment portion where the developing blade 42and the developing sleeve 41 abut against each other, the toner T iselectrically charged by friction (triboelectricity) and is alsoregulated in toner layer thickness. Thereafter, the toner T is conveyedto a developing area 31 (FIG. 1) where the photosensitive drum 1 and thedeveloping sleeve 41 face each other.

A predetermined developing bias (developing voltage) is applied to thedeveloping sleeve 41 from a developing power source (high voltage powersource) which is provided in the apparatus main body 110 to serve asvoltage applying means. The developing bias applied in the embodiment isan oscillation voltage created by superimposing a DC voltage (forexample, Vdc=−400 V) on an AC voltage (for example, peak-to-peakvoltage=1,500 Vpp, frequency f=2,400 Hz). The photosensitive drum 1 iselectrically grounded. An electric field is thus generated in thedeveloping area 31 where the photosensitive drum 1 and the developingsleeve 41 face each other. The action of the electric field causes thetoner T conveyed to the developing area 31 to transfer to the surface ofthe photosensitive drum 1 in accordance with an electrostatic latentimage on the surface of the photosensitive drum 1. The electrostaticlatent image on the photosensitive drum 1 is developed with the toner Tas a result. In the embodiment, an electrostatic latent image isdeveloped by adhering the toner T which is charged to the same polarityas the charge polarity of the photosensitive drum 1 (the negativepolarity) to an exposed part (image part) on the photosensitive drum 1which has been uniformly charged and then exposed to light to be therebydecayed in the absolute value of the electric potential (a reversaldevelopment method).

While the description of the embodiment uses an example in which anelectrostatic latent image is developed with a magnetic single-componentdeveloper (toner) charged to a negative polarity, a nonmagneticdeveloper or a two-component developer may be used instead. Thedeveloper may also be charged to a positive polarity instead of anegative polarity in developing.

IV. Detecting Device

A description will be provided of the detecting device (developer amountdetecting device) 130 which uses the capacitance detection method andwhich serves as detecting means (developer amount detecting means) fordetecting the amount of developer in the embodiment.

The detecting device 130 of the embodiment includes the developingsleeve 41 as a first electrode, the antenna member 43 as a secondelectrode, a developing power source 131, a capacitance detectingcircuit 132, a controller portion 133, and the like. The antenna member43 is arranged on a surface of the developing frame 40 and has a surfaceopposed to the developing sleeve 41. The antenna member 43 in theembodiment is formed on a flat surface portion for the ease ofmanufacturing. The amount of the toner T in the developer containingportion 40 a is determined based on the capacitance between thedeveloping sleeve 41 and the antenna member 43. The capacitancedetecting circuit 132 and the controller portion 133 together constitutea remaining developer amount detecting device (toner remaining amountdetecting device) 134. A more detailed description will be providedbelow.

In the embodiment, the developing sleeve 41 doubles as the firstelectrode (input-side electrode) configured to detect the capacitance.The antenna member 43 which is a capacitance detecting member isprovided as the second electrode (output-side electrode or oppositeelectrode) configured to detect the capacitance. The antenna member 43in the embodiment is constituted by a conductive resin sheet which is aconductive resin member. The antenna member 43 has a part that isrectangular in plan view and that has a predetermined length in thelongitudinal direction, which is substantially parallel to thelongitudinal direction (rotation axis direction) of the developingsleeve 41, and a predetermined length in the lateral direction, whichintersects (substantially orthogonal in the embodiment) the longitudinaldirection of the antenna member 43. The rectangular part is ameasurement part which forms the surface opposed to the developingsleeve 41 in the embodiment. The antenna member 43 may have a partconfigured to form a conductive path and other parts in addition to themeasurement part configured to form the surface that is opposed to thedeveloping sleeve 41. For instance, the part configured to form aconductive path may be formed at an end portion of the rectangularmeasurement part in the longitudinal direction in a continuous manner asa single sheet. The conductive resin sheet is, as described in detaillater, a sheet-shaped member of a monolayer structure or a multi-layerstructure which is resin-based and is conductive. The antenna member 43is arranged on a part of the bottom of the toner chamber 46 b formed bythe developing frame 40 so that changes can be detected in the amount ofthe toner T between a surface of the antenna member 43 which is opposedto the developing sleeve 41 and the developing sleeve 41. The antennamember 43 in the embodiment is flat.

When an AC voltage (AC bias) is applied to the developing sleeve 41, acurrent which is determined in relation to the capacitance between thedeveloping sleeve 41 and the antenna member 43 is induced between thetwo. The capacitance varies depending on the amount of the toner Tbetween the developing sleeve 41 and the antenna member 43.Specifically, the detected capacitance is large when the amount of thetoner T between the electrodes is large, because a relative permittivityof the toner T is larger than a relative permittivity of the air. Thevalue of the current flowing into the antenna member 43 is measured, viaa contact point (not shown) provided in the process cartridge 120 and acontact point (not shown) provided in the apparatus main body 110, bythe capacitance detecting circuit 132 which is provided in the apparatusmain body 110. In the embodiment, the capacitance detecting circuit 132generates a voltage signal in relation to this current value (namely,capacitance value) and inputs the voltage signal to the controllerportion 133 provided in the apparatus main body 110. The controllerportion 133 can obtain the amount of the toner T from the input voltagesignal based on information (a data table or the like) indicating arelation between the capacitance and the amount of the toner T which isset in advance.

Based on the obtained amount of the toner T, the controller portion 133can inform a user of information related to the amount of the toner T bydisplaying the information on a display portion of the apparatus mainbody 110 which serves as informing means, a monitor of the personalcomputer connected to the apparatus main body 110. The user is thusprompted to prepare a new process cartridge 120.

FIG. 4 is a graph showing a relation between the amount of the toner Tin the developer containing portion 40 a and the capacitance in theembodiment. In the embodiment, the antenna member 43 is provided on thebottom of the toner chamber 46 b, and a change in the amount of thetoner T between the developing sleeve 41 and the antenna member 43 isdetected. Detected in the embodiment are changes in the amount of thetoner T from a time point where the toner T has been consumed some andthe amount of the toner T in the developer containing portion 40 a isaround 150 g to the depletion of the toner T. The image formingapparatus 100 of the embodiment can thus notify the user or others ofthe amount (remaining amount) of the toner T sequentially during thisperiod. The detection range of the remaining amount of the toner Tvaries depending on the arrangement of the antenna member 43, and theantenna member 43 may therefore be arranged in any desired place. Theantenna member 43 may be arranged in the toner chamber 46 b or in thedeveloping chamber 46 a.

The length in the longitudinal direction of the antenna member 43 in theembodiment is substantially the same as the extent of an image area (adirection substantially orthogonal to an image conveying direction).This is because, even when the amount of the toner T is uneven in thelongitudinal direction, the detection precision is improved by detectingthe capacitance in a wide range which includes the uneven part. Thelength in the longitudinal direction of the antenna member 43 maytherefore be longer than the extent of the image area. However, if sodesired, the antenna member 43 having the length which is shorter in thelongitudinal direction than the extent of the image area may be arrangedin, for example, the central portion of the image area or around an endportion of the image area. This applies, for example, when it isacceptable in terms of detection precision, when the agitating member 45prevents unevenness in the amount of the toner T in the longitudinaldirection, and when the unevenness in the amount of the toner T in thelongitudinal direction (or a defect in the image due to the unevenness)itself is detected by the capacitance detection method. Alternatively, aplurality of conductive resin members of different lengths may beprovided in the longitudinal direction of the developing sleeve 41 sothat an uneven toner distribution or the toner amount is detected bydetecting a plurality of differences or differentials in capacitancebetween the developing sleeve 41 and the conductive resin members.Instead of the plurality of conductive resin members of differentlengths, a component whose length in the lateral direction (width)gradually decreases from one end to the other end in the longitudinaldirection may be used to detect differences in capacitance.

The length in the lateral direction of the antenna member 43 may belonger or shorter than the one in the embodiment. For example, in thecase of detecting the remaining amount of the toner T in a wider range,the length in the lateral direction of the antenna member 43 may be setlonger than in the embodiment. The antenna member 43 in this case is notlimited to the bottom of the toner chamber 46 b and may cover anarbitrary stretch of the surface of the developing frame 40. To giveanother example, in the case of detecting with high precision theremaining amount of the toner T in a particular range such asimmediately before the depletion of the toner T, the antenna member 43may have the length in the lateral direction set shorter than in theembodiment so as to be closer to the developing sleeve 41.

In the embodiment, the developing sleeve 41 serves as an AC voltageinput portion (input-side electrode) configured to detect the amount ofthe toner T because an AC voltage is applied to the developing sleeve 41in image forming, and the antenna member 43 serves as an output portion(output-side electrode) for the detection. The developing frame 40 inthe embodiment therefore has a holding portion configured to hold thedeveloping sleeve 41. The AC voltage input portion is not limited to thedeveloping sleeve 41, and can be any conductive member. The developingframe 40 in this case has a holding portion configured to hold theconductive member. Alternatively, the electrode constituted by aconductive resin sheet may serve as the AC voltage input portion(input-side electrode). In this case, an AC voltage is applied from anAC voltage source via the contact point provided in the processcartridge 120 and the contact point provided in the apparatus main body110 to the electrode constituted by a conductive resin sheet.

The detecting device described in the embodiment detects the capacitancebetween the developing sleeve 41 and the electrode. However, the presentinvention is not limited thereto and both of the paired electrodes maybe conductive resin members. In other words, the developer amount may bedetected from a difference in capacitance between the conductive resinmembers (FIG. 13). The present invention in this case can also beapplied to the remaining toner amount detection for a nonmagnetic tonerwhich is used in a full-color image forming apparatus to which aplurality of cartridges are detachably mountable.

V. Manufacturing Method

A method of manufacturing the developer container 46 in the embodimentwill be described next.

As mentioned above, methods that have been used to manufacture adeveloping container of which the developer amount is detected by thecapacitance detection method include ones in which an antenna member isstuck to a frame with double-sided adhesive tape, or deposited on theframe by evaporation, or printed on the frame. However, such methodsrequire a step of performing post-processing on the frame after theframe is formed and accordingly tend to complicate the manufacturingsteps. In addition, the method that uses double-sided adhesive tape tostick the antenna member to the frame, for example, has a risk of lowdetection precision due to variations in the sizes and positions of therespective parts.

A possible alternative method is to use as an antenna member aplate-shaped metal member (such as SUS sheet metal) which is inserted toa resin-made frame when the frame is molded. This method, however,presents difficulties in design because the molded resin shrinkssignificantly when cooled whereas the plate-shaped metal member does notcontract much, which easily leads to the distortion of the resultantcontainer. The method also requires providing a location where theantenna member and the frame are fixed to each other (a fixing portionor a fixing shape). For example, the method requires preventing theantenna member from moving by molding the frame so that the fixingportion of the frame covers an end surface and both surfaces of theantenna member at an end portion in the longitudinal direction of theantenna member. This means that the frame itself needs to be thick andthat the frame tends to be large because the frame is likely to have acomplicated shape with surface irregularities in a location where themold and the frame are fixed. Moreover, this method does not make fulluse of the performance of the plate-shaped member because the fixingportion configured to fix the antenna member which has a shape withsurface irregularities turns what is originally an area where a changein developer amount causes a change in capacitance into an area wherethe capacitance does not change.

Using a resin electrode (conductive portion) as the electrode configuredto detect capacitance, on the other hand, is advantageous in terms ofmanufacturing process simplification and detection precision improvementbecause the electrode can easily and precisely be molded by a relativelysimple method that uses a mold. As described later, using a resinelectrode is also advantageous in that the cost of the electrode itselfis reduced and in that a drop in detection precision due to a magneticdeveloper clinging to the electrode is prevented.

For example, it is conceivable to form a conductive portion on the framefrom a conductive resin by two-color molding. This method, however,requires a molding step twice and therefore still has room forimprovement for simpler manufacturing. With a method in which theelectrode layer is provided on a sheet member as described above forpreventing the developer from scattering, the manufacturing steps tendto be complicated because of a step of attaching the sheet member to theframe of the developing apparatus.

Thus, a simple way to manufacture a developer container of which thedeveloper amount is detected by the capacitance detection method isdemanded. A manufacturing method that accomplishes high-precisiondetection of the developer amount is also sought after.

The embodiment addresses the issue by, prior to the molding of thedeveloping frame 40, first holding a conductive resin sheet from whichthe antenna member 43 is constructed in a mold and then injecting aresin (synthetic resin) to be formed into the developing frame 40, intothe mold. The developing frame 40 to which the antenna member 43 isintegrally fixed is molded in this manner. A more detailed descriptionthereof will be provided below.

The embodiment uses as a conductive resin sheet 24 a polystyrene (PS)resin sheet on one surface of which is coated with a conductivematerial, specifically, carbon, to have conductivity. The surface of theconductive resin sheet 24 which is coated with carbon is referred to assurface A (FIGS. 6A and 6B). A surface of the conductive resin sheet 24which is opposite to the surface A and where the PS resin is exposed isreferred to as a surface B. The surface A of the conductive resin sheet24 is brought into contact with the mold when the developing frame 40 ismolded in the embodiment. In this manner, at least a part of (in theembodiment, substantially the entirety of) the surface of the conductiveresin sheet 24 which is brought into contact with the mold is a surfaceof the antenna member 43 opposed to the developing sleeve 41. At leastthe surface B of the conductive resin sheet 24 is brought into contactwith the resin injected into the mold when the developing frame 40 ismolded in the embodiment. In the embodiment, a PS resin is exposed alsoon a side end surface between the surface A and the surface B, and theside end surface is also brought into contact with the resin injectedinto the mold when the developing frame 40 is molded.

FIGS. 5A, 5B, 5C, and 5D schematically illustrate steps of manufacturingthe developing frame 40 in the embodiment. The developing frame 40 maybe constructed by coupling a plurality of frame parts which have beenmolded. The developing frame 40 in the embodiment is constructed bycoupling a lower frame 40A, which forms the bottom of the developercontaining portion 40 a, and an upper frame 40B, which is put on thelower frame 40A like a lid, as illustrated in FIG. 3. The lower frame40A and the upper frame 40B are molded separately from each other. Theantenna member 43 in the embodiment is arranged in the lower frame 40A,and FIGS. 5A to 5D therefore schematically illustrate lower framemanufacturing steps (hereinafter the lower frame 40A may simply bereferred to as “developing frame 40”).

As illustrated in FIG. 5A, a mold 201 of an injection molding machine200 has a first mold 202 (or a male mold (core)) and a second mold 203(or a female mold (cavity)). The first mold 202 has a surface 221 forforming the containing portion-side surface of the developing frame 40.The second mold 203 has a surface 231 for forming a surface of thedeveloping frame 40 which is opposite to the developer containingportion 40 a (the outer surface of the developing frame 40). Minute airholes (air suction portions) 222 are provided in a predetermined holdingarea Y of the first mold 202, the holding area Y being used for holdingthe conductive resin sheet 24. A suction device 204 is connected to theminute air holes 222 to suction air in a direction indicated by an arrowS1 of FIG. 5A. The second mold 203 is provided with a gate 232.

To mold the developing frame 40 with the injection molding machine 200,the conductive resin sheet is first arranged in the holding area Y sothat the surface A of the conductive resin sheet 24 is in contact withthe surface 221 of the first mold 202 as illustrated in FIG. 5B, and airsuction by the suction device 204 is put into operation. The surface Aof the conductive resin sheet 24 is suctioned and held onto the surface221 of the first mold 202 in this manner.

Thereafter, as illustrated in FIG. 5C, the first mold 202 and the secondmold 203 are closely pressed to each other with a desired pressurizingforce to create a cavity portion where the developing frame 40 isformed. A thermoplastic resin for forming the developing frame 40 isinjected from the gate 232 in a direction indicated by an arrow S2 inFIG. 5C. The injected thermoplastic resin is cooled to be cured(solidified), thereby forming the developing frame 40 to which theantenna member 43 constituted by a conductive resin sheet is integrallyfixed. As the thermoplastic resin injected into the mold 201, theembodiment uses a high impact polystyrene (HIPS) resin which hascompatibility with at least the surface B (and the side end surface aswell in the embodiment) of the conductive resin sheet 24. By injectingand curing the resin into the mold 201, the antenna member 43constituted by a conductive resin sheet is molded integrally with thedeveloping frame 40.

Thereafter, air suction by the suction device 204 is stopped and thedeveloping frame 40 to which the antenna member 43 has integrally beenfixed can be taken out of the mold 201 as illustrated in FIG. 5D.

The lower frame 40A molded in the manner described above is coupled tothe separately molded upper frame 40B by any suitable fixing method suchas thermal welding. The developer container 46 formed from thedeveloping frame 40 can thus be manufactured. The developing sleeve 41and other components of the developing apparatus 4 described above areattached to (held by) the developer container 46 before and/or after theupper frame 40B and the lower frame 40A are coupled, to therebymanufacture the developing apparatus (developing unit) 4. The cleaningunit 12 described above is coupled to (held by) the developing apparatus(developing unit) 4, to thereby manufacture the process cartridge 120.

In the embodiment, a metal contact point is pressed against a conductiveportion (not shown) at an end portion of the developing frame 40 inwhich the antenna member 43 is integrally molded. A conductive memberwhich is connected to, or continued from, the contact point on one endis led out and laid around the process cartridge 120 so that the otherend of the conductive member serves as a point of contact with theapparatus main body 110. Consequently, a current flowing in the antennamember 43 when an AC voltage is applied to the developing sleeve 41during image forming is detected by the capacitance detecting circuit132, which is provided in the apparatus main body 110, as describedabove.

VI. Effects

According to the embodiment, the developing frame 40 in which theantenna member 43 is integrally molded can be manufactured by a simplemethod having fewer steps in which the conductive resin sheet 24 is heldby suction to the mold 201 (the first mold 202) in advance when thedeveloping frame 40 is molded.

FIG. 6A is a sectional view of a part of the developing frame 40 whichis in the vicinity of the antenna member 43 at the center in thelongitudinal direction of the antenna member 43 (a section along thelateral direction of the antenna member 43). As described above, in theembodiment, at least the surface B (and the side end surface as well inthe embodiment) of the conductive resin sheet 24 has compatibility withthe thermoplastic resin injected into the mold 201. Accordingly, atleast the surface B (and the side end surface as well in the embodiment)of the conductive resin sheet 24 is integrated with a thermoplasticresin injected into the mold in the molding of the developing frame 40.The formed developing frame 40 is therefore already one with which theantenna member 43 is integrated, and there is no need to further processthe developing frame 40 into a special shape configured to fix theantenna member 43.

The capacitance value is known to change in proportion to the reciprocalnumber of the distance between two electrodes. This is not an issue inthe embodiment where the conductive resin sheet 24 is held during themolding so that the surface A of the conductive resin sheet 24 which isa surface opposed to the developing sleeve 41 is in contact with thesurface of the mold 201 (the first mold 202). This substantiallyprevents variations in the position of the surface A due to, forexample, variations in the thickness of the conductive resin sheet 24and the way the conductive resin sheet 24 is fixed. With variations inthe distance between the two electrodes thus prevented, capacitancevariations are reduced and high-precision detection of the amount of thetoner T is accomplished.

According to the embodiment, the entirety of the surface B of theconductive resin sheet 24 is substantially uniformly and integrallyfixed to the developing frame 40. The embodiment is therefore free fromthe partly falling off of the antenna member 43 due to the distortion ofthe developer container 46 which is caused when, for example, anexternal force is applied temporarily, and from the resultant reductionin the precision of the detection of the amount of the toner T.

The embodiment uses suction via air suction as a method of holding theconductive resin sheet 24 onto the mold 201. However, the presentinvention is not limited thereto, and, for example, electrostatic force,magnetic force, gravity, or any other binding force may be used as longas the conductive resin sheet 24 can be held onto the mold 201 in adesired place. For instance, the conductive resin sheet 24 may be heldby use of grease. However, holding by air suction is preferred for thereason that it is easily carried out without needing special materialsand other reasons. While substantially the entirety of the conductiveresin sheet 24 is suctioned by air suction in the embodiment, providingthe air holes 222 in at least a part of the mold surface in contact withthe conductive resin sheet 24 which is closer to the gate 232 helps inpreventing the positional gap of the conductive resin sheet 24 duringresin injection into the mold 201.

The conductive resin sheet 24 in the embodiment has, at least on theside of the developing frame 40 (the frame side), a surface constitutedby a material which has compatibility with the thermoplastic resininjected into the mold 201 when the developing frame 40 is molded (thesurface B and the side end surface in the embodiment). Compatibility ingeneral means a property in which two or more different substances haveaffinity with one another and mix practically homogeneously withoutinducing a chemical reaction to form a solution or a mixture.Compatibility here means a property in which a material can be fixed tothe developing frame 40 by dissolution or mixing that takes place in atleast a part of the boundary between the material and the resin injectedinto the mold 201 under conditions (temperature, time, and the like)logical for the developing frame molding method described above. Thesame material as the resin injected into the mold 201, or a differentmaterial that has this property, is a material that has compatibility.However, the present invention is not limited thereto and the conductiveresin sheet 24 may have, at least on the side of the developing frame40, a surface constituted by a material which has adhesiveness to theresin injected into the mold 201 when the developing frame 40 is molded.Adhesiveness in general means a property in which two surfaces arebonded to each other by one of or both of a chemical force and aphysical force. Adhesiveness here means a property in which a materialis fixed to the developing frame 40 by other actions than in the case ofmaterials that have the compatibility described above, in the boundarybetween the material and the resin injected into the mold 201 underconditions (temperature, time, and the like) logical for the developingframe molding method described above. The conductive resin sheet 24 hereonly needs to include a material which has compatibility with oradhesiveness to the injected resin, and there is no need to strictlydiscern which of compatibility and adhesiveness is at work in fixing theconductive resin sheet 24 to the developing frame 40.

In the case where the resin injected into the mold 201 is an HIPS resin,for instance, examples of materials which are compatible with the resininclude a PS resin, an HIPS resin, and a PS resin dispersed with carbonand an HIPS resin dispersed with carbon which are obtained bydispersing, for example, carbon black as a conductive material in a PSresin and an HIPS resin, respectively. Examples of materials which arenot compatible with but are adhesive to the HIPS resin injected into themold 201 include an ethylene vinyl acetate (EVA) resin and EVA dispersedwith carbon in which, for example, carbon black is dispersed as aconductive material.

The surface of the conductive resin sheet 24 which has compatibilitywith or adhesiveness to the resin injected into the mold 201 does notalways need to be the entirety of the surface of the conductive resinsheet 24 which is on the side of the developing frame 40 (in theembodiment, substantially the entirety of the surface B andsubstantially the entirety of the side end surface). The conductiveresin sheet 24 may have neither of compatibility and adhesiveness in apart of its surface on the side of the developing frame 40 as long asthe antenna member 43 is fixed well to the developing frame 40. From theviewpoint of better prevention of the falling of the antenna member 43off the developing frame 40, however, it is preferred for the surface Bof the conductive resin sheet 24 which is opposite to the surface A (thesurface opposed to the other electrode) of the conductive resin sheet 24to be compatible with or adhesive to the resin injected into the mold201. In this case, the surface B can be partially compatible or adhesivebut, more desirably, has compatibility or adhesive substantiallythroughout.

The conductive resin sheet 24 may be conductive on one of or both of thesurface A and the surface B. The conductive resin sheet 24 can have anystructure that has (in the case of the output-side electrode) or thatcan establish (in the case of the input-side electrode) electricalconnection between the conductive portion of the antenna member 43 andthe capacitance detecting circuit 132 when installed as the antennamember 43 in the developing frame 40. The conductive resin sheet 24installed as the antenna member 43 in the developing frame 40 only needsto have a level of conductivity which is sufficient as an electrodeconfigured to detect the developer amount by the capacitance detectionmethod. The conductive resin sheet 24 which has a two-layer structureincluding a conductive layer in the embodiment may therefore have athree-layer structure that includes at least one conductive layer. Theconductive resin sheet 24 is not limited to a sheet-shaped member whichhas a synthetic resin-based multilayer structure, and may be a syntheticresin-based, monolayer, sheet-shaped member which has conductivity. Forexample, the conductive resin sheet 24 can be a conductive sheet-shapedmember which is formed from a resin in which carbon black is dispersedas a conductive material. The resin (base) which is the base of thisconductive resin sheet 24 has compatibility with or adhesiveness to theresin which is injected into the mold 201 when the developing frame 40is molded. The conductive resin sheet 24 thus has compatibility with oradhesiveness to the resin which is injected into the mold 201 when thedeveloping frame 40 is molded, at least on the side of the developingframe 40 (usually the entirety).

The conductive resin sheet 24 having a multilayer structure which is asheet-shaped member made of a PS resin with a carbon coat in theembodiment is not limited thereto. For example, the conductive resinsheet 24 can be a resin-made, sheet-shaped member which is coated withother conductive substances than carbon, or a resin-made, sheet-shapedmember on which a conductive substance is deposited by evaporation orprinted. The conductive resin sheet 24 can also have a two-layerstructure in which a protective layer configured to prevent nicks isformed on a surface of a conductive sheet-shaped member, or athree-layer structure in which a PS resin base is sandwiched betweenconductive layers which are obtained by dispersing a conductive materialsuch as black carbon in a PS resin. Also in these cases, similarly tothe embodiment, the resin-made sheet member (base) is formed from amaterial which has compatibility with or adhesiveness to the resin whichis injected into the mold 201 when the developing frame 40 is molded(FIGS. 12A, 12B, and 12C).

It is preferred for the conductive resin sheet 24 to be constituted by anonmagnetic or diamagnetic sheet-shaped member so that, when a magnetictoner is used, the toner T which is a magnetic substance does not clingto the conductive resin sheet 24.

The conductive material is not limited to carbon black, and any materialwhich gives conductivity to the conductive resin sheet 24, such asgraphite, a carbon fiber, or a carbon nanotube, can be used.

VII. Shrinking of Conductive Resin Sheet

The developing frame 40 shrinks when molded or after removed from themold 201. When shrinking, the developing frame 40 sometimes warps if theYoung's modulus of the conductive resin sheet 24 is larger than theYoung's modulus of the HIPS resin forming the developing frame 40 whichis 3.5 GPa. If this phenomenon changes the distance between the antennamember 43 constituted by the conductive resin sheet 24 and thedeveloping sleeve 41 more than acceptable, it is conceivable that theprecision drops in the detection of the amount of the toner T.

The warping of the developing frame 40 is a phenomenon which is causedby the shrinking of the developing frame 40, which takes place at thetime of the molding of the developing frame 40 or after the removal ofthe developing frame 40 from the mold 201, in the case where theconductive resin sheet 24 used is greater in Young's modulus than amaterial that forms the developing frame 40. In other words, theshrinking of the developing frame 40 at the time of molding or afterremoval from the mold 201 is accompanied by the shrinking of theconductive resin sheet 24. However, in the case where the conductiveresin sheet 24 is greater in Young's modulus than the material of thedeveloping frame 40 and there is a difference in the amount of shrinkagebetween the developing frame 40 and the conductive resin sheet 24, theconductive resin sheet 24 cannot absorb, by distortion or the like, theshrinkage of the developing frame 40. For instance, when the developingframe 40 shrinks in directions indicated by arrows A of FIG. 6B (adirection running along the lateral direction of the conductive resinsheet 24), shrinking occurs in directions indicated by arrows B of FIG.6B (a direction running along the lateral direction of the conductiveresin sheet 24) in the vicinity of the conductive resin sheet 24. Theshrinkage in the directions of the arrows B of FIG. 6B is smaller inamount than the shrinkage in the directions of the arrows A of FIG. 6B,and it is conceivable that a phenomenon in which the developing frame 40warps in a direction indicated by an arrow C of FIG. 6B (the side wherethe amount of shrinkage is larger) therefore occurs in this case. Thephenomenon of the warping of the developing frame 40 did not occur whenthe Young's modulus of the conductive resin sheet 24 which is an EVAsheet dispersed with carbon black is set to 2.5 GPa to 3.5 GPa bychanging the dispersion of carbon black. The phenomenon of the warpingof the developing frame 40 did not occur also when the conductive resinsheet of the embodiment is used which is a PS resin sheet coated withcarbon (Young's modulus=2.5 GPa). Similarly, the phenomenon of thewarping of the developing frame 40 did not occur when the conductiveresin sheet 24 used is a PS resin sheet which is dispersed with carbonso as to have a Young's modulus of 3.5 GPa, and when the conductiveresin sheet 24 used is an EVA sheet which is dispersed with carbon so asto have a Young's modulus of 0.2 GPa.

From these facts, the conductive resin sheet 24 whose Young's modulus isequal to or smaller than the Young's modulus of the resin forming thedeveloping frame 40 is preferred for use in the embodiment. In short, itis preferred for the conductive resin sheet 24 to have a Young's modulusequal to or less than that of the resin forming the developing frame 40.More desirably, the conductive resin sheet 24 is smaller (for example,1/10 or less) in Young's modulus than the resin forming the developingframe 40 because, then, the shrinkage of the conductive resin sheet 24follows the shrinkage of the developing frame 40 more closely. In thecase where the resin forming the developing frame 40 is an HIPS resin(Young's modulus=3.5 GPa), for instance, a conductive resin sheet 24which is an EVA sheet dispersed with carbon black (Young's modulus=0.2GPa) or a similar sheet can be used favorably.

VIII. Comparison Between Examples and Comparative Examples

The superiority of the embodiment will be described next with the use ofcomparative examples. In the comparative examples, components that havefunctions and configurations equivalent to those of the embodiment aredenoted by the same reference symbols.

Configuration of Example 1

Example 1 is as described in the first embodiment.

Configuration of Comparative Example 1

FIG. 7A is a sectional view of a part of the developing frame 40 whichis in the vicinity of an antenna member 47 according to ComparativeExample 1 at the center in the longitudinal direction of the antennamember 47 (a section along the lateral direction of the antenna member47). In Comparative Example 1, the antenna member 47 which is aplate-shaped member formed from stainless steel (SUS) (SUS sheet metal)is stuck to the molded developing frame 40 with double-sided adhesivetape 48. In other words, the method of manufacturing the developercontainer 46 according to Comparative Example 1 has a step of stickingthe prepared antenna member 47 with the double-sided adhesive tape 48 tothe developing frame 40 that has been molded.

Superiority of Example 1 to Comparative Example 1

Comparative Example 1 requires a step of fixing the antenna member 47 tothe developing frame 40, which has been molded, by the double-sidedadhesive tape 48. In contrast, the developing frame 40 in which theantenna member 43 is integrally molded is obtained in Example 1 merelyby holding by suction the conductive resin sheet 24 onto the mold 201when the developing frame 40 is molded. Example 1 accordingly needsfewer steps than Comparative Example 1 to manufacture the developingframe 40 which has the antenna member 43.

In addition, the position of the antenna member in Comparative Example 1can fluctuate because of variations in the thickness of the double-sidedadhesive tape 48 and the thickness of the antenna member 47. In Example1, on the other hand, variations in the thickness of the antenna member43 cause practically no variations in the position of the antenna member43 because the surface A of the antenna member (conductive resin sheet)43 is held so as to be in contact with the mold 201. Example 1 istherefore higher in the precision of the distance between the antennamember 43 and the developing sleeve 41 than Comparative Example 1, andcan detect the amount of the toner T with high precision.

Configuration of Comparative Example 2

FIG. 7B is a sectional view of a part of the developing frame 40 whichis in the vicinity of the antenna member 47 according to ComparativeExample 2 at the center in the longitudinal direction of the antennamember 47 (a section along the lateral direction of the antenna member47). Further, FIG. 7C is a similar diagram in an end portion in thelongitudinal direction of the antenna member according to ComparativeExample 2. In Comparative Example 2, the antenna member 47 which is SUSsheet metal is inserted when the developing frame 40 is molded.

Comparative Example 2 does not use the double-sided adhesive tape 48 tofix the antenna member 47 as in Comparative Example 1, and the antennamember 47 in Comparative Example 2 is therefore not stuck to the resinof the developing frame 40. In Comparative Example 2, the antenna member47 is fixed to the developing frame 40 by providing a fixing portion (ora fixing shape) 49 in a part of the developing frame 40 which is at theend portion in the longitudinal direction of the antenna member 47 asillustrated in FIG. 7C. The fixing portion 49 in Comparative Example 2is molded so as to cover the end surface and both surfaces (the surfaceA and the surface B) of the antenna member 47 at the end portion in thelongitudinal direction of the antenna member 47.

Superiority of Example 1 to Comparative Example 2

A thickness “t” of the developing frame 40 at the end portion in thelongitudinal direction of the antenna member 47 in Comparative Example 2is thicker than in Example 1. In addition, Comparative Example 2involves providing the fixing portion 49 which is formed from a resinbetween the developing sleeve 41 and the antenna member 47. Providingthe fixing portion 49 where changes in capacitance which accompany theconsumption of the toner T do not take place can lower the precision inthe detection of the amount of the toner T in Comparative Example 2because the detection of the amount of the toner T using changes incapacitance is achieved by detecting changes in the capacitance betweenthe electrodes which accompany the consumption of the toner T. Incontrast, Example 1 has no need for providing a member equivalent to thefixing portion 49 and therefore has no fear of low precision in thedetection of the toner T which is caused by the reason described above.

The detaching (partly falling off) of the antenna member 47 from thedeveloping frame 40 is also a possibility with Comparative Example 2when a change in atmospheric temperature or the application of anexternal force causes distortion. In Example 1, on the other hand, theantenna member (conductive resin sheet) 43, which is substantiallyuniformly and integrally fixed to the developing frame 40 on the surfaceB, does not detach from the developing frame 40. This is presumablybecause the force which fixes the resins to each other is strong. Thedistance between the developing sleeve 41 and the antenna member 43 isthus kept stable and the amount of the toner T is detected with steadyprecision. Accordingly, the precision in the detection of the amount ofthe toner T does not easily drop.

Configuration of Example 2

Example 2 is configured according to the first embodiment, but differsfrom Example 1 in the shape of the antenna member 43.

FIG. 8 is a schematic sectional view of the developing apparatus 4according to Example 2, which is a modification example of Example 1.FIG. 8 schematically illustrates function blocks that constitute thedetecting device 130 as well.

The developing frame 40 in Example 2 is not straight (flat) on thesurface where the antenna member 43 is provided as illustrated in FIG.8. However, a conductive resin sheet from which the antenna member 43 isconstructed has flexibility in Example 2 and, when the developing frame40 is molded, can therefore be held by air suction or the like to asurface of the mold 201 as in Example 1 even though the surface of themold 201 configured to mold the developing frame 40 is curved asillustrated in FIG. 8. The conductive resin sheet can similarly be fitalong the mold surface by other methods than air suction as describedabove. The resin sheet constituting the antenna member 43 in Example 1can also have flexibility.

Thus, as the conductive resin sheet constituting the antenna member 43has flexibility, the antenna member can easily be arranged on a curvedsurface of the developing frame 40. This enables the image formingapparatus 100 to detect the remaining amount of the toner T over a widerrange by, for example, arranging the antenna member 43 in a broaderstretch of the curved bottom of the toner chamber 46 b.

Superiority of Example 2

A case where an antenna member formed from SUS sheet metal is insertedwhen the developing frame 40 is molded is considered for example. Theantenna member is fixed by the same method which is used in ComparativeExample 2 described above. In this case, where the antenna member isformed from SUS sheet metal which does not have flexibility, SUS sheetmetal is machined in advance to have a shape that fits the curved shapeof a part of the developing frame 40 where the antenna member is to bearranged, and the shaped SUS sheet metal is set in a mold and subjectedto insert molding. In short, this case requires machining in advance SUSsheet metal into a shape which fits the shape of the relevant part ofthe developing frame 40. In addition, because tolerance is setrespectively in curve machining of the mold and curve machining of theSUS sheet metal, the SUS sheet metal may not fit closely to the curve ofthe mold, thereby creating a gap between the mold and the SUS sheetmetal. This can lower the precision of the distance between the antennamember and the developing sleeve 41.

In Example 2, on the other hand, the developing frame 40 which includesthe antenna member 43 can be molded merely by holding a conductive resinsheet onto a curved surface of the mold as in Example 1 without allowingthe precision of the distance between the antenna member 43 and thedeveloping sleeve 41 to drop.

Second Embodiment

A second embodiment of the present invention will be described next. Inthe second embodiment, components whose functions and configurations arethe same as, or equivalent to, those in the first embodiment are denotedby the same reference symbols, and detailed descriptions thereof areomitted.

Described in the embodiment are electrical characteristics of aresin-made antenna member which are preferred in order to improvedetection precision when the developer amount is detected by thecapacitance detection method using the antenna member.

I. Developing Apparatus

FIG. 9 is a schematic sectional view of the developing apparatus 4 inthe embodiment. The developing apparatus 4 has the developing frame 40which forms the developer container 46 configured to contain the toner Tas a developer, and which supports components described later. The tonerT in the embodiment is a developer having a mean particle size of 7 μm.The developing frame 40 in the embodiment is formed from high impactpolystyrene (HIPS).

The developing sleeve 41 in the embodiment is formed by coating asurface of an aluminum-made sleeve which is a nonmagnetic body with aresin layer of intermediate resistance which has a thickness of 10 μm.The volume resistance of the resin layer is approximately 1 to 10Ω.

The magnet roller 44 which serves as magnetic field generating means isarranged in the cavity portion of the developing sleeve 41. The magnetroller 44 is supported by the developing frame 40 in a fixed manner(irrotationally). The magnet roller 44 in the embodiment has a pluralityof magnetic poles (in the embodiment, four magnetic poles denoted by S1,N1, S2, and N2) which are arranged so that N-poles and S-poles alternatein the circumferential direction (FIGS. 20A and 20B). The magnetic poleS1 is a developing pole which is arranged in a place opposed to thephotosensitive drum 1 to control the development of an electrostaticlatent image by the toner T. The magnetic pole N1 is a regulating polewhich is arranged in a place opposed to the developing blade 42, whichwill be described later, to control the amount of the toner T on thedeveloping sleeve 41. The magnetic pole S2 is a supplying pole (intakepole) which supplies the toner T in the developer container 46 onto thedeveloping sleeve 41. The magnetic pole N2 is a toner leak preventingpole (sealing pole) which is arranged where a spouting preventing sheet32 configured to prevent the leakage of the toner T from the developercontainer 46 is provided. The magnetic poles are kept in the samedirection all the time because the magnet roller 44 does not rotate andis held at a fixed position all the time.

The developing blade 42 which is a regulating member is arranged in thedeveloping chamber 46 a so as to abut against the circumferentialsurface of the developing sleeve 41, and serves as developer layerthickness regulating means. The developing blade 42 in the embodiment isformed by fixing, by adhesion, a urethane rubber blade which is aplate-shaped member formed from an elastic material to supporting sheetmetal, and the supporting sheet metal is fixed to the developing frame40. The urethane rubber blade is thus brought into contact with thedeveloping sleeve 41 at an appropriate abutting pressure to control thelayer of the toner T on the developing sleeve 41 to a proper thicknessand charge the toner layer by friction. The regulating member may beformed from a material that shields magnetism, a resin, or the like. Thedeveloping chamber 46 a is also provided with the spouting preventingsheet 32 which is a sheet-shaped member configured to prevent thespouting of the toner. The spouting preventing sheet 32 abuts againstthe developing sleeve 41 along an edge of the opening 46 c which isopposite to where the developing blade 42 is provided.

In the embodiment, the antenna member 43 constituting the detectingdevice 130, which will be described later, is arranged on a part of thebottom of the developing chamber 46 a.

In the toner chamber 46 b, on the other hand, the agitating member 45 isprovided to serve as developer agitating means. The agitating member 45includes the support rod 45 a and the agitating sheet 45 b, which isfixed to the support rod 45 a. The support rod 45 a is supportedrotatably by the developing frame 40 at both end portions in thelongitudinal direction of the support rod 45 a (a rotation axisdirection). A rotational driving force is transmitted to the agitatingmember 45 from the drive motor (not shown) which is provided in theapparatus main body 110 to drive and rotate the agitating member 45 in adirection indicated by an arrow X3 of FIG. 9. The support rod 45 a inthe embodiment rotates once in approximately one second. The agitatingsheet 45 b in the embodiment is a PPS sheet (a sheet-shaped memberformed from a polyphenylene sulfide resin) having a thickness of 100 μm,and is fixed to the support rod 45 a at one end portion in the lateraldirection of the agitating sheet 45 b by being press-fit or weldedthereto. In the embodiment, the length in the longitudinal direction ofthe agitating sheet 45 b is 216 mm. With the rotational driving of theagitating member 45, the toner T contained in the toner chamber 46 b isconveyed from the toner chamber 46 b to the developing chamber 46 athrough the toner supply opening 46 d, which is an opening forcommunication between the developing chamber 46 a and the toner chamber46 b.

The toner T conveyed to the developing chamber 46 a reaches the vicinityof the developing sleeve 41, is attracted to the developing sleeve 41 bythe magnetic pole S2 of the magnet roller 44, and is supplied to thesurface of the developing sleeve 41. The toner T supplied to thedeveloping sleeve 41 by the magnetic force of the magnetic pole S2 isconveyed by the developing sleeve 41 and regulated by the developingblade 42. At this point, the toner T passing through a regulatingportion is charged by friction. An electrostatic latent image formed onthe photosensitive drum 1 is developed with the toner T that has passedthe regulating portion. The toner T that has been regulated by thedeveloping blade 42, on the other hand, is divided into one which isheld by the magnetic pole N1 to stay in the vicinity of the developingblade 42 and one which is flung out of the reach of the magnetic forceof the magnetic pole N1. The toner T that has been flung is agitated bythe agitating member 45 and then supplied to the developing sleeve 41again in the case where the remaining amount of the toner T in thedeveloper container 46 is large. In the case where the remaining toneramount in the developer container 46 is small, the toner T that has beenflung drops vertically and lands in the vicinity of the antenna member43. The dropped toner T is pushed out by the toner T that is moved thereby the agitating member 45, without clinging to the antenna member 43.Alternatively, the dropped toner T is attracted by the magnetic force ofthe magnetic pole S2 to be supplied to the developing sleeve 41 again.

A predetermined developing bias (developing voltage) is applied to thedeveloping sleeve 41 from the developing power source 131 (high voltagepower source) which is provided in the apparatus main body 110 to serveas voltage applying means. The developing bias applied in the embodimentis an oscillation voltage created by superimposing a DC voltage Vdc of−400 V on an AC voltage Vpp of 1,400 V (frequency=2,000 Hz, arectangular wave). The photosensitive drum 1 is electrically grounded.An electric field is thus generated in the developing area 31 where thephotosensitive drum 1 and the developing sleeve 41 face each other.

The toner supply opening 46 d is blocked (sealed) by the sealing member48 (FIG. 16) until the sealing member is removed at the time of startingusing the process cartridge 120 in order to prevent toner leakage duringthe shipping of the process cartridge 120 or the like. The sealingmember 48 in the embodiment is a PS resin sheet, and is adhered insidethe developer container 46 so as not to allow the toner T to escape aregion illustrated in FIG. 9 for the prevention of toner leakage inshipping or the like.

II. Detecting Device

The detecting device 130 of the embodiment will be described next. FIG.9 is a schematic sectional view of the developing apparatus 4 that alsoillustrates function blocks of the detecting device 130 of theembodiment. The basic configuration and operation of the detectingdevice 130 in the embodiment are substantially the same as in the firstembodiment.

In the embodiment, the antenna member 43 which serves as the secondelectrode (output-side electrode, opposite electrode) is arranged on apart of the bottom of the developing chamber 46 a formed by thedeveloping frame 40. The antenna member 43 detects a change in theamount of the toner T which is present between a surface of the antennamember 43 which is opposed to the developing sleeve 41 and thedeveloping sleeve 41. In the embodiment, the developing sleeve 41 isused as one of the pair of electrodes as in the first embodiment, butanother electrode may be provided instead of using the developing sleeve41 as an electrode of the remaining toner amount detecting means. Thedegree of freedom in design about the arrangement of the electrode ishigher in this case. In other words, the developer container or thedeveloping apparatus needs at least an antenna member configured todetect the developer amount (toner amount) with the use of capacitance.

III. Regarding Antenna Member

The antenna member 43 of the embodiment is formed from a nonmagnetic ordiamagnetic conductive resin sheet so that the toner which is a magneticsubstance does not cling to the antenna member 43, and is arranged so asto face a vertically lower side of the developing sleeve 41.Specifically, the antenna member 43 is fixed by adhesion through insertmolding to the bottom of the inner wall of the developer container 46,in the vicinity of the developing sleeve 41. The conductive sheet memberconstituting the antenna member 43 is provided so as to partiallyoverlap with a part of the developing sleeve 41 in the direction of thegravity (a region A in FIG. 9) when attached to the developer container46 in order to detect capacitance more accurate capacitance. In thisconfiguration where the antenna member 43 is located in the vicinity ofa spot below the developing sleeve 41 and the toner accordingly tends tobuild up on the electrode surface due to gravity, the effect broughtabout by using a conductive resin sheet which contains a resin in thatthe remaining toner amount can be measured accurately is particularlypronounced. This is because the clinging of a magnetic toner due to themagnetic force does not occur with a conductive resin sheet whichcontains a resin. The conductive resin sheet is provided below thedeveloping sleeve 41 in the gravity direction in the embodiment, too.However, the antenna member 43 can be used also when the electrodes arearranged side by side in a horizontal direction with respect to thedeveloper carrying member as disclosed in, for example, Japanese PatentApplication Laid-Open No. 2007-264612. As described later in detail, theconductive resin sheet is arranged so as to come into contact with acontact point (not shown) which is located on the bottom of thedeveloper container 46 on the near side in the drawing sheet of FIG. 9,and is connected to an earth via the toner remaining amount detectingdevice 134, which is provided in the apparatus main body 110.

In the configuration described above, the toner remaining amountdetecting device 134 can detect the capacitance between the developingsleeve 41 and the antenna member 43 by applying bias to the developingsleeve 41 from the developing power source 131. The configuration of theembodiment performs sequential remaining amount detection in whichcapacitance is detected sequentially during printing.

FIGS. 12A, 12B, and 12C are sectional views of the conductive resinsheet 24. Described here are a configuration in which a carbon materialis dispersed in a resin, a configuration in which resin layers includingdispersed carbon material sandwich another resin layer, and aconfiguration in which a developer carrying member-side surface of aresin layer is coated with a carbon material.

FIG. 12A illustrates the conductive resin sheet 24 that has athree-layer structure in which a resin layer of a PS resin 24 d issandwiched between conductive layers 24 c (each having a thickness of 20μm to 40 μm) in which carbon black is mixed and dispersed in a PS resin.In this case, the conductive layers 24 c are electrode portions and theconductive resin sheet 24 as a whole is an electrode. Electricalconnection to the outside can be as follows. Specifically, cutting theconductive resin sheet 24 distorts and connects the conductive layers 24c of both surfaces, and an external electrical contact point isconnected to where the conductive layers 24 c are connected. Anotheroption is to use the conductive resin sheet 24 that has a one-layerstructure (monolayer structure) in which carbon black 24 e is mixed withan EVA resin 24 d as illustrated in FIG. 12B. In this case, the entireconductive resin sheet 24 is an electrode portion. The conductive resinsheet 24 of FIG. 12C can also be used which has a two-layer structureobtained by printing carbon black 24 e on a PS resin 24 d.

The embodiment uses a flexible monolayer conductive resin sheet 24 ofFIG. 12B in which carbon black 24 e is dispersed in a base made of EVA.The content of carbon black 24 e dispersed in EVA when expressed inweight percent concentration is 35 (30 to 40) wt. %. As a countermeasurefor spike current which will be described later, the content ofdispersed carbon black 24 e is set so that the resistance is 10³ to 10⁵Ωwhen measured by a measurement method described later. It is preferredto use the conductive resin sheet 24 whose total thickness “t” is 0.05to 0.3 mm from the ease of the processing of adhering the conductiveresin sheet 24, although depending on the shape of a surface of thedeveloper container 46 to which the conductive resin sheet 24 isadhered. The total thickness “t” in the embodiment is 0.1 mm. While anexample of using carbon black as a carbon material which givesconductivity is described here, the conductivity may be given by othercarbon materials than carbon black, such as graphite, a carbon fiber, ora carbon nanotube.

FIG. 14A is a plan view that illustrates the antenna member 43 of theembodiment in more detail. The antenna member 43 in the embodiment has apart which is rectangular in plan view and that has a predeterminedlength in the longitudinal direction, which is substantially parallel tothe longitudinal direction (rotation axis direction) of the developingsleeve 41, and a predetermined length in the lateral direction, whichintersects (substantially orthogonal in the embodiment) the longitudinaldirection of the antenna member 43. In order to obtain electricalconnection from an end portion, which is far from the developing sleeve41, in the lateral direction of the rectangular part at an end portionof the rectangular part on the near side in the drawing sheet of FIG. 9to a contact point (not shown) in the apparatus main body 110, theconductive resin sheet 24 is extended to the outside of the developercontainer 46. In short, a rectangular area of the antenna member 43 inthe embodiment is a measurement portion 43A as illustrated in FIG. 14A.An extended area of the antenna member 43 which is enclosed by a dottedline in FIG. 14A is a contact point portion 43B, which serves as anelectrical contact point between the antenna member 43 and the apparatusmain body 110. The contact point portion 43B is connected to an earthvia a contact point with the apparatus main body 110 (not shown) and thetoner remaining amount detecting device 134 arranged in the apparatusmain body 110. FIGS. 15A and 15B are perspective views illustrating thedeveloping frame 40 (the lower frame 40A, in particular) of theembodiment. FIG. 15A illustrates the inside of the developer container46, and FIG. 15B illustrates the outside of the developer container 46.As illustrated in FIGS. 15A and 15B, the measurement portion 43A of theantenna member 43 is arranged in the developing frame 40 so as to facethe developing sleeve 41, whereas the contact point portion 43B isarranged outside the developing frame 40. The conductive resin memberforms the contact point portion 43B on the outside by extending to theoutside through the inside of the developing frame 40. In theembodiment, the two frames are welded by ultrasonic welding. A part ofthe conductive resin member is passed through the thickness of thedeveloping frame 40 toward the outside at a point inside the weldedportion so as to be arranged outside the developing frame 40. The partof the conductive resin member which is exposed outside the developingframe 40 extends from inside the welded portion, goes around the weldedportion, and reaches outside the welded portion. In this manner, thecontact point portion 43B can be formed without being affected by thewelded portion.

In the embodiment, the width in the longitudinal direction of therectangular measurement portion 43A of the antenna member 43 (L1 in FIG.14A) is 216 mm, which is a length dimension of a guaranteed printingarea (image area), and the width of the measurement portion 43A in thelateral direction which is a direction perpendicular to thislongitudinal direction is 15 mm. The antenna member 43 in the embodimenthas a thickness of 100 μm.

The embodiment uses insert molding, with which the antenna member 43 canbe fixed by compatibility or adhesion to the inner wall of the developercontainer 46 more precisely in terms of position precision in thearrangement of the conductive resin sheet 24, than when double-sidedadhesive tape is used to fix the antenna member 43. As a result, theprecision of the distance between the developing sleeve 41 and theantenna member 43 which are electrodes improves, which leads to animprovement in the precision of developer amount detection. The fixingmethod according to the first embodiment is particularly preferred.

On the other hand, in the case where the conductive resin sheet 24 whichis made of EVA is molded in the developer container 46 by insertmolding, a difference in the amount of thermal shrinkage between theconductive resin sheet 24 and the developer container 46 may cause thefollowing phenomena. The first phenomenon occurs when the developercontainer 46 is larger in shrinkage amount than the conductive resinsheet 24, and the conductive resin sheet 24 may be undulated aftercooling. The precision of the distance to the developing sleeve 41consequently drops, which lowers the precision of developer amountdetection. The second phenomenon is the distortion of the developercontainer 46 which occurs when the conductive resin sheet is larger inshrinkage amount than the developer container 46 and the rigidity of thedeveloper container 46 is smaller than the shrinking force of theconductive resin sheet 24. The precision of the distance to thedeveloping sleeve 41 consequently drops, which lowers the precision ofdeveloper amount detection. The spouting preventing sheet 32 is alsoundulated, thereby letting the toner leak.

The above-mentioned phenomena are prevented by, for example, making theconductive resin sheet 24 larger in shrinkage amount than the developercontainer 46 and making the rigidity of the developer container 46larger than the shrinking force of the conductive resin sheet 24. Inthis way, the molding may be completed while keeping the conductiveresin sheet 24 pulled in close contact with the developer container 46.It has been found as a result of study that the conditions given aboveare satisfied by forming the conductive resin sheet 24 which has aYoung's modulus of 0.2 to 0.3 GPa and a thickness of 0.1 mm when thedeveloper container 46 is formed from HIPS to have a Young's modulus of2.5 to 3.5 GPa and a thickness of 1.5 mm. With these settings, themolding can be completed without an undulation of the conductive resinsheet 24 and without a distortion of the developer container 46, whilemaintaining the precision of the distance to the developing sleeve 41,and the precision of developer amount detection is accordingly improved.In view of the above, the thickness and Young's modulus of theconductive resin sheet 24 in the embodiment are set to 0.1 mm and 0.25GPa.

The conductive resin sheet 24 can be formed from any resin which adheresto the developer container 46 and which does not allow a magnetic tonerto cling thereto. In the case where the developer container 46 which isused is made from HIPS, the conductive resin sheet 24 may be formed fromPS instead of EVA. The conductive resin sheet 24 can also have anyconfiguration as long as the configuration includes a conductive layerin which carbon black is dispersed in a surface layer, which comes intocontact with the toner to be measured, of the conductive layer, and thesame effect is obtained also with a sheet which has a multilayerconfiguration such as the ones illustrated in FIG. 12A and FIG. 12C.

It is preferred to arrange the conductive resin sheet 24 so that theconductive resin sheet 24 in the lateral direction is in the vicinity ofthe developing sleeve 41. This is because the toner that has beenregulated by the developing blade 42 and dropped down is detected as aremaining toner as well with high precision.

IV. Comparison between Examples and Comparative Examples

Configuration of Example 3

Example 3 is configured according to the second embodiment. Theresistance of the conductive resin sheet 24 in Example 3 which ismeasured by a measurement method (1) which will be described later isequal to or less than 10⁵Ω (10³ Ω, 10⁴ Ω, 10³ Ω, 0Ω).

Configuration of Comparative Example 3

Comparative Example 3 differs from Example 3 in the antenna member 43.The antenna member 43 used in Comparative Example 3 is SUS 304, which isobtained by machining a SUS metal by rolling to a thickness of 500 μmand cutting the SUS into a strip which measures 216 mm in thelongitudinal direction and 15 mm in the lateral direction. The SUS 304which is originally nonmagnetic is magnetized when stress appliedthereto causes martensitic transformation of the austenitic phase. Theantenna member 43 of Comparative Example 3 is also magnetized as aresult of stress applied by rolling and cutting.

Example 4

Example 4 is configured according to the second embodiment but differsfrom Example 3 in the antenna member 43. The shape, material, and fixingmethod of the antenna member 43 in Example 4 are the same as in Example3, except that an amount of carbon black dispersed in an EVA resin ofthe conductive resin sheet 24 is lessened in Example 4. The resistanceof this conductive resin sheet 24 which is measured by the measurementmethod (1) described later is 10⁶Ω.

(Evaluation Method)

The remaining toner amount is obtained by a remaining toner amountcalculating method described below.

FIG. 10 is an example of a relation between the remaining toner amountand the capacitance according to the second embodiment. The axis ofordinate indicates capacitance detected by the toner remaining amountdetecting device 134, and the axis of abscissa indicates the remainingtoner amount (%). With the configuration of the second embodiment, thecapacitance does not change during a time period between an initialpoint (100%) and a 20% (broken line A). This is because the remainingtoner amount is large enough not to cause a change in toner amount(developer amount) between the developing sleeve 41 and the antennamember 43. When the remaining toner amount becomes equal to or less than20%, the capacitance decreases linearly with the reduction in remainingtoner amount. This indicates that the toner amount (developer amount)between the developing sleeve 41 and the antenna member 43 is changingwith changes in remaining toner amount.

A difference between capacitance C₀ and capacitance C_(s) is given asΔE₀. The capacitance C₀ represents the capacitance of when the cartridgeis new and there is no toner between the developing sleeve 41 and theantenna member 43. The capacitance C_(s) represents the capacitance in aperiod between the time when the remaining toner amount is 100% (full)and the time when the remaining toner amount is 20%. When an averagevalue of capacitance measured while one sheet of image is printed isoutput as capacitance C, a difference between capacitance during imageprinting and the capacitance C₀ which is the capacitance of when thereis no toner between the developing sleeve 41 and the antenna member 43is given as ΔE. Then the current remaining toner amount is calculated bythe following Expression (1).Current remaining toner amount=20%×ΔE/ΔE ₀  Expression (1)

The detection result is notified to the user by displaying the result onthe display portion of the image forming apparatus 100, a monitor 21 ofthe personal computer, or the like.

(Evaluation Result)

<Comparison in Remaining Toner Amount Detection Precision BetweenExample 3 and Comparative Example 3>

FIG. 11A shows a relation between the remaining toner amount and thecapacitance that were actually measured or output in an endurance testconducted on Example 3. FIG. 11B shows a relation between the remainingtoner amount and the capacitance which were actually measured or outputin an endurance test conducted on Comparative Example 3. The axis ofabscissa indicates the amount of toner which is actually remaining inthe developer container 46, and the axis of ordinate indicates thecapacitance.

In FIG. 11A which is a graph of Example 3, the capacitance does notchange when the remaining toner amount is 100% to 20%. The capacitancedecreases linearly with the reduction in remaining toner amount in anarea where the remaining toner amount is equal to or less than 20%. Atthe time of “1” in FIG. 11A, an image in which a toner is not developedin a vertical belt pattern (hereinafter also referred to as “image witha blank area”) was generated. No toner clinging to the antenna member 43at that time and, consequently, shaking the developing apparatus 4 atthe time of “1” did not remedy the blank area.

Similarly to Example 3, the capacitance in Comparative Example 3 doesnot change when the remaining toner amount is 100% to 20% as shown inFIG. 11B. The capacitance decreases linearly with the reduction inremaining toner amount in an area where the remaining toner amount isequal to or less than 20%. However, an image with a blank area wasgenerated at the time (“2” in FIG. 11B) when the remaining toner amountwas larger than in Example 3. It was confirmed that toner clinged to theantenna member 43 at that time. Although the amount of toner (developer)remaining between the electrodes is the same, the toner clinging to theantenna member 43 cannot be used for development. Consequently, a blankarea occurred at the time of “2” where the detected toner amount(developer amount) was large.

The toner has clung to the antenna member 43 because the antenna member43 is magnetized. After the toner clinging to the antenna member 43 wassuctioned, the remaining toner amount was measured again to reveal thatthe remaining toner amount detected was “3”, which was the same as inExample 3. An image generated at that time had a blank area similarly tothe image generated at the time of “2”. Thus, when an image with a blankarea is generated in Comparative Example 3 varies depending on theamount of toner clinging to the antenna member 43. In addition, how muchtoner clings to the antenna member 43 varies from one developingapparatus to another, which lowers the precision of remaining toneramount detection.

The test shows that, in Example 3 where no toner clinged to the antennamember 43 at the time of “1”, a full proportion of the toner between theelectrodes is effectively put into use. In other words, a drop in theprecision of remaining toner amount detection due to the clinging oftoner to the antenna member 43 is prevented and the precision isimproved in remaining toner amount detection.

<Comparison in Remaining Toner Amount Detection Precision BetweenExample 3 and Example 4>

Table 1 shows a relation between the resistance of the conductive resinsheet measured by a measurement method (1) which will be described laterand the precision of remaining toner amount detection. A symbol “∘”registered for “remaining amount detection” indicates that the remainingtoner amount was detected with precision, and a symbol “Δ” registeredfor “remaining amount detection” indicates that, although the remainingtoner amount was detected, performing signal processing or the like ispreferred because the detection signal was small. A symbol “x”registered for “remaining amount detection” indicates that the remainingtoner amount was not detected successfully.

Table 1 shows that the precision of remaining toner amount detection isfavorable in Example 3, where the resistance of the conductive resinsheet is 10⁵Ω or less. When the resistance of the conductive resin sheetis 10⁶Ω or more as in Example 4, on the other hand, the detection signalis small and signal processing of some kind is necessary in order tograsp the capacitance accurately. This is because the high resistance ofthe conductive resin sheet reduces a current that flows into the tonerremaining amount detecting device 134, which makes it difficult for thetoner remaining amount detecting device 134 to detect capacitance. Theresistance of the conductive resin sheet is therefore desirably 10⁵Ω orless. The resistance value per unit length in this case was 420 Ω/mm.

TABLE 1 Relation between conductive sheet resistance measured bymeasurement method (1) and remaining toner amount detection precisionResistance [Ω] Remaining amount detection Example 4 10⁶ Δ Example 3 10⁵∘ 10⁴ ∘ 10³ ∘ 0 ∘

Configuration of Example 5

Example 5 is configured according to the second embodiment. Theresistance of the conductive resin sheet 24 in Example 5 which ismeasured by a measurement method (2) which will be described later isequal to or more than 10³Ω.

FIG. 13 illustrates a toner remaining amount detecting circuit as theone disclosed in, for example, Japanese Patent Application Laid-Open No.2007-264612. The toner remaining amount detecting circuit does not havea mechanism for reducing the amount of current flowing in the tonerremaining amount detecting circuit (a protective resistor) when spikecurrent such as fluctuations caused by the application of an AC voltageflows. A detector of the toner remaining amount detecting device 134consequently has a fear of malfunction. Example 5 therefore focusesattention also on a solution for the malfunction of the detector whichis caused by spike current.

The antenna member 43 in Example 4 was adjusted in the amount anddistribution of carbon black so that the resistance measured by themeasurement method (2) which will be described later was equal to ormore than 10³Ω (10³ Ω, 10⁴Ω).

Configuration of Comparative Example 4

The antenna member 43 of Comparative Example 4 was the SUS 304 which iscommonly used. The resistance of the SUS 304 measured by the measurementmethod (2) which will be described later was 0Ω.

Evaluation Result Comparison in Spike Current Reduction Between Example5 and Comparative Example 4

Table 2 shows a relation between the resistance measured by themeasurement method (2) which will be described later and a spike currentreducing effect. The relation of the symbols “∘”, “Δ”, and “x” in Table2 is the same as in Table 1.

Table 2 shows that the precision of remaining toner amount detection andthe spike current reducing effect were both favorable when theresistance of the conductive resin sheet was 10³Ω or more. Theresistance value per unit length in this case was 30 Ω/mm. InComparative Example 4, where the resistance was 0Ω), the spike currentreducing effect was low and a drop in the precision of remaining toneramount detection by the toner remaining amount detecting device 134 wasa possibility.

TABLE 2 Relation between conductive sheet resistance measured bymeasurement method (2) and spike current reducing effect Resistance [Ω]Spike current reduction Example 5 10⁴ ∘ Comparative 10³ ∘ Example 4 0 ×

It is concluded from the results of Examples 3 to 5 that spike currentcan be reduced while maintaining the precision of remaining toner amountdetection by setting the conductive resin sheet resistance which ismeasured by the measurement method (1) to 10³Ω or less and setting theconductive resin sheet resistance which is measured by the measurementmethod (2) to 10³Ω or more. In short, it is preferred to set theresistance of the conductive resin sheet to 10³Ω or more and 10⁵Ω orless.

V. Conductive Resin Sheet Resistance Measurement Method

Methods of measuring the resistance of a conductive resin sheet in thesecond embodiment will be described.

The conductive resin sheet resistance varies depending on the distancefrom a contact point. The conductive resin sheet resistance is thereforedefined by the following two measurement methods.

<Measurement Method (1)>

The resistance between a measurement point A and a measurement point Bwhich are illustrated in FIG. 14B is measured. The measurement point Ais a tip end portion in the contact point portion 43B (a surface on thesame side as a surface of the measurement portion 43A that comes intocontact with developer). The measurement point B is a point in themeasurement portion 43A (the surface that comes into contact withdeveloper) which is farthest from the measurement point A (themeasurement point B is a point on the side of the developing sleeve 41in the lateral direction). Conductive grease is applied to each of themeasurement points in a circular pattern having a diameter of 5 mm, andthe resistance between the measurement point A and the measurement pointB is measured with the use of Fluke 87V manufactured by Fluke Inc.

<Measurement Method (2)>

The resistance between the measurement point A and a measurement point Cwhich are illustrated in FIG. 14B is measured. Similarly to the above,the measurement point A is a tip end portion in the contact pointportion 43B (the surface on the same side as the surface of themeasurement portion 43A that comes into contact with developer). Themeasurement point C is a point in the measurement portion 43A (thesurface that comes into contact with developer) which is closest fromthe measurement point A (the measurement point C is a point on the sideof the developing sleeve 41 in the lateral direction). Conductive greaseis applied to each of the measurement points in a circular patternhaving a diameter of 5 mm, and the resistance between the measurementpoint A and the measurement point C is measured with the use of Fluke87V manufactured by Fluke Inc.

While the clinging of a magnetic toner to the electrode is regarded as aproblem in the second embodiment, the second embodiment has aconfiguration which is novel in itself, and allows the use of aconductive sheet as a remaining toner amount detecting member which usescapacitance even with a nonmagnetic toner which does not cause theproblem of clinging.

Third Embodiment

A third embodiment of the present invention will be described next. Inthe third embodiment, components whose functions and configurations arethe same as, or equivalent to, those in the first and second embodimentsare denoted by the same reference symbols, and detailed descriptionsthereof are omitted.

In the embodiment, a description will be provided of the arrangement ofa resin-made antenna member which is preferred in order to improvedetection precision of the developer amount by the capacitance detectionmethod with the use of the antenna member.

I. Developing Apparatus

FIG. 16 is a schematic sectional view of the developing apparatus 4 inthe embodiment.

The sealing member 48 in the third embodiment is adhered to, forexample, a seal welding rib 47 which is provided on a part of the bottomof the developer containing portion 40 a which is in the vicinity of thetoner supply opening 46 d. Therefore, in the case where the bottom ofthe developer containing portion 40 a is flat, the seal welding rib 47may hinder the circulation of the toner T from the toner chamber 46 b tothe developing chamber 46 a. The third embodiment avoids this byproviding a convex portion 46 e between the developing sleeve 41 and theagitating member 45, which is as tall as, or taller than, the sealwelding rib 47 when the developing apparatus 4 is in use. The convexportion 46 e in the third embodiment is provided on a part of the bottomof the toner chamber 46 b which is adjacent to the toner supply opening46 d. The convex portion 46 e projects toward the interior of thedeveloper container 46 and also projects toward the developing sleeve41. The convex portion 46 e enables the agitating member 45 to move thetoner T toward the vicinity of the developing sleeve 41 without a hitch,despite the presence of the seal welding rib 47. A part of the bottom ofthe toner chamber 46 b which is opposite to the developing sleeve 41with respect to the convex portion 46 e has a concave portion 46 f. Theagitating sheet 45 b enters the concave portion 46 f to an appropriatedegree when the agitating member 45 is driven and rotated. The toner Tmoved by the agitating sheet 45 b toward the convex portion 46 e isflung by the agitating sheet 45 b which has just been released aroundthe peak of the convex portion 46 e, and is thus moved to the vicinityof a part of the surface of the developing sleeve 41 that corresponds tothe magnetic pole S2 of the magnet roller 44. In this manner, the tonerT deposited on the bottom of the toner chamber 46 b can be conveyed tothe vicinity of the developing sleeve 41 more securely. The sealingmember 48 in the third embodiment is attached to an agitating shaft ofthe agitating member 45.

II. Detecting Device

The detecting device 130 of the embodiment will be described next. Thebasic configuration and operation of the detecting device 130 in theembodiment are substantially the same as in the first and secondembodiments.

FIG. 17 illustrates the schematic flow of processing of detecting theamount (remaining amount) of the toner T and informing the user orothers of the detected amount. First, the controller portion 133 startsan image printing operation (S101). The controller portion 133 nextobtains a capacitance measurement result which is measured by thecapacitance detecting circuit 132 during image printing (S102). Thecontroller portion 133 then refers to the capacitance detection resultand the data table to obtain the current remaining amount of the toner T(S103). The controller portion 133 next informs a user of informationrelated to the obtained remaining amount of the toner T (S104) bydisplaying the information on the display portion (not shown) which isprovided in the apparatus main body 110, or the monitor 21 of thepersonal computer 20.

As the data table for obtaining the current remaining amount of thetoner T from the capacitance detected by the capacitance detectingcircuit 132, capacitance transitions accompanying the consumption of thetoner T are obtained in advance, such as transitions indicated by thesolid line in FIG. 19, which will be described later. This informationin the third embodiment is stored in a process cartridge-side memory 13(FIG. 2) which is provided in the process cartridge 120. The relationbetween the amount of the toner T and the capacitance can be obtainedby, for example, as follows. Each time a predetermined amount of thetoner T is poured sequentially into the developer container 46 which isempty in the beginning, the process cartridge 120 which includes thedeveloper container 46 is loaded in the image forming apparatus 100 toperform a pre-multi-rotation operation, and the capacitance detectingcircuit 132 then measures the capacitance. The pre-multi-rotationoperation is a preparatory operation which is performed after the imageforming apparatus 100 is powered on and before the image formingapparatus 100 is ready for image formation.

III. Configuration and Manufacturing Method of Antenna Member

It was found as a result of study conducted by the inventors of thepresent invention that the precision of developer amount detectiondropped in some cases even though a conductive resin sheet which servedas a resin electrode was molded integrally with a developing frame byinsert molding. For instance, there was a case where the depletion ofdeveloper was indicated despite the fact that a relatively large amountof developer was still left. The reason thereof is as follows.Specifically, the conductive resin sheet which has been set in a moldwith high position precision for the molding of the developing frame isheated by the heat of an injected resin and shrinks thermally in acooling (curing) step. As a result, the position precision varies in anend portion of the conductive resin sheet, which changes the distancebetween the end portion of the conductive resin sheet and the developingsleeve serving as the other electrode. Capacitance detection thus yieldsdifferent results for the same developer amount, and the precision ofdeveloper amount detection drops accordingly.

The third embodiment addresses this by setting the arrangement of theantenna member 43 so that the precision in the detection of the amountof the toner T is prevented from dropping even when the distance betweenthe antenna member 43 and the developing sleeve 41 varies as describedabove. Details of the arrangement will be described later.

FIG. 18 is a sectional view of a part of the mold 201 configured to moldthe developing frame 40 which is in the vicinity of where the conductiveresin sheet 24 constituting the antenna member 43 is arranged. In thethird embodiment, the air suction portion 222 is provided in an endportion of the conductive resin sheet 24 on the side of the gate 232,and the conductive resin sheet 24 is suctioned to the first mold 202 inthis end portion. This facilitates the prevention of wrinkles due to thestretching of the conductive resin sheet 24 by heat from a resininjected into the mold 201, and the prevention of misalignment due tothermal shrinkage of the conductive resin sheet 24 during cooling. Forthe positioning by air suction, it is only necessary to ensure that theconductive resin sheet 24 cannot be moved by the pressure of theinjected resin, and substantially the entire surface of the conductiveresin sheet 24 may be suctioned by air suction.

The conductive resin sheet 24 in the third embodiment is a monolayerstructure conductive resin sheet which is given conductivity bydispersing carbon black as a conductive material in a base made of EVA.The conductive resin sheet 24 that has a multilayer structure generallyhas a thin conductive layer. It is therefore advisable to be carefulwith friction that occurs when, for example, a metal contact point isbrought into contact with the conductive resin sheet 24 in order toobtain electrical connection to a grounding pole.

The measurement portion of the conductive resin sheet 24 in the thirdembodiment is substantially rectangular. The length in the longitudinaldirection of the measurement portion is 216 mm, which is the same as thedimension of the image area (guaranteed printing area) in a directionsubstantially orthogonal to the image conveying direction. The length inthe lateral direction of the measurement portion is 40 mm. Theconductive resin sheet 24 has a thickness of 100 μm. The developingframe 40 (in particular, the bottom of a part of the developercontaining portion 40 a which is in the vicinity of the antenna member43) has a thickness of 1.5 mm.

IV. Arrangement of Antenna Member

The arrangement of the antenna member 43 will be described next. Thereis a possibility that the position of the antenna member 43 may beshifted even when the manufacturing methods described above are used.The chance of misalignment is particularly high for an end portion ofthe antenna member 43 in the lateral direction which is a directionintersecting (in the third embodiment, substantially orthogonal to) thelongitudinal direction (axial direction) of the developing sleeve 41,which serves as the other electrode. This is because of tolerance forthe installation position of the conductive resin sheet 24 set in themold 201 (the first mold 202), tolerance for the shape distortion(thermal shrinking and the like) of the conductive resin sheet 24 thatoccurs in the process from the injection of a resin into the mold 201 tothe cooling, and others. The precision in the detection of the amount ofthe toner T tends to drop when the position of an end portion B isshifted. The end portion B is an end portion of the antenna member 43which is closer to the developing sleeve 41 when viewed in thelongitudinal direction (axial direction) of the developing sleeve 41,and which is on the side of the developing sleeve 41 in the lateraldirection (FIG. 18).

In the third embodiment, the distance between the developing sleeve 41and the end portion B, which is not positioned by air suction, tends tochange significantly in the lateral direction of the antenna member 43,compared to the other end portion of the antenna member 43 (an endportion which is on the side of the gate 232 when molded) (FIG. 18).

The third embodiment addresses this by setting the arrangement of aclosest point A as illustrated in FIG. 21A. The closest point A is apoint on the antenna member 43 where the antenna member 43 is closest tothe developing sleeve 41 as viewed along the longitudinal direction(axial direction) of the developing sleeve 41. Specifically, the closestpoint A is arranged in other places than an end portion of the antennamember 43 (to be exact, the end portion B which is closer to thedeveloping sleeve 41).

In this way, the precision in the detection of the amount of the toner Tis prevented from dropping even when the distance between the antennamember 43 and the developing sleeve 41 varies because of the shrinkingof the conductive resin sheet 24 or the like.

V. Effects

(Relation Between Way of Toner Deposition and Detected Capacitance)

FIG. 19 shows a relation between the remaining toner amount and thecapacitance. The axis of abscissa indicates the remaining toner amountand the axis of ordinate indicates the detected capacitance. Thecapacitance which is detected when the remaining toner amount is 0% isrepresented by C₀. In the third embodiment, the user is informed oftoner depletion (out of toner) when the capacitance reaches C₀ onaccount that an image with a blank area may be generated at that point.

The solid line in FIG. 19 represents the relation between the remainingtoner amount and the capacitance which is obtained in advance in theconfiguration of the third embodiment in the manner described above. Thebroken line in FIG. 19 represents a relation between the amount of toneractually remaining in the developer container 46 and the detectedcapacitance when the distance between the antenna member 43 and thedeveloping sleeve 41 becomes larger because of, for example, apositional gap of the antenna member 43. A differential between thesolid line and the broken line is given as ΔC. When the broken line isbelow the solid line, the distance between the antenna member 43 and thedeveloping sleeve 41 is widened and the capacitance which is detectedfor the same remaining toner amount is accordingly lower. When thecapacitance C₀ is detected, the remaining toner amount indicated by thesolid line is 0%. The remaining toner amount indicated by the brokenline, on the other hand, is not 0% and is larger by ΔM. Thus, a changein the distance between the antenna member 43 and the developing sleeve41 causes a change in capacitance by ΔC with respect to the remainingtoner amount. The change in capacitance results in a difference of ΔM inthe remaining toner amount when the capacitance C₀ is detected.

In FIG. 19, the capacitance is constant irrespective of the remainingtoner amount in a zone 1 where the remaining toner amount is m1 to m2.FIG. 20A is a schematic sectional view of a part of the developercontainer 46 which is in the vicinity of the antenna member 43, andschematically illustrates the way the toner deposits in the developercontainer 46 in this zone. FIG. 20A is viewed in the longitudinaldirection (rotation axis direction) of the developing sleeve 41 (thesame applies to FIGS. 20B, 21A, 22A, 23A, 24A, and 25A). Broken lines R1and R2 in FIG. 20A each represents a tangent line of the developingsleeve 41 that passes through an end portion in the lateral direction ofthe antenna member 43. An area enclosed by the broken line R1, thebroken line R2, the surface of the developing sleeve 41, and the surfaceof the antenna member 43 is a remaining toner amount measurement area(the same applies to FIGS. 20B, 21A, 22A, and 23A). In FIG. 20A, tonersurface levels are respectively represented by H1 and H2. The tonersurface level is at H1 when the process cartridge 120 is new, andgradually shifts to H2 as the toner is consumed by forming images. Untilthe toner surface level reaches H2, the remaining toner amountmeasurement area is filled with the toner and the capacitance istherefore constant irrespective of the remaining toner amount. The tonerin the zone 1 circulates from an arrow T1 to an arrow T2 and then to anarrow T3 (T1→T2→T3). Specifically, the toner moved by the agitatingmember 45 to the vicinity of the developing sleeve 41 is supplied to thesurface of the developing sleeve 41 by the magnetic pole S2 of themagnet roller 44 (the arrow T1). The toner supplied to the surface ofthe developing sleeve 41 is conveyed by the rotation of the developingsleeve 41 to a portion where the developing blade 42 and the developingsleeve 41 abut against each other (the arrow T2). The toner which isregulated by the developing blade 42 and scraped off the surface of thedeveloping sleeve 41 is returned to the toner chamber 46 b by theagitating member 45 (the arrow T3).

Next, the capacitance decreases with the reduction of the remainingtoner amount in a zone 2 of FIG. 19 where the remaining toner amount ism2 to 0%. FIG. 20B is a schematic sectional view of a part of thedeveloper container 46 which is in the vicinity of the antenna member43, and schematically illustrates the way the toner deposits in thedeveloper container 46 in this zone. In FIG. 20B, toner surface levelsare respectively represented by H3 and H4. The toner surface level is atH3 and H4 around the time when the remaining toner amount is less thanm2 in FIG. 19. The toner surface level is at H4 right before an imagewith a blank area is generated. The toner surface level H3 is in thetoner remaining amount measurement area, and the capacitance thereforedecreases from then on with the consumption of the toner. The tonerultimately deposits in the vicinity of the area where the developingsleeve 41 and the developing blade 42 abut against each other asindicated by the toner surface level H4, because of the action of themagnetic poles of the magnet roller 44. The toner in the zone 2circulates as in the zone 1 and, additionally, some toner drops down tothe vicinity of the antenna member 43 as indicated by an arrow t4. Whenthe toner surface level reaches H4 ultimately, the toner circulates onlywithin the toner deposit in the vicinity of the area where thedeveloping sleeve 41 and the developing blade 42 abut against eachother, from an arrow t1 to an arrow t2 and then to an arrow t3(t1→t2→t3), with the rotation of the developing sleeve 41.

(Positional Relation Between Antenna Member and Developing Sleeve)

Variations in the position of the antenna member 43 lead to variationsin capacitance detection result. The capacitance detection sensitivityis higher when the distance between the developing sleeve 41 and theantenna member 43 is closer. Therefore, a particularly high precision isdemanded for the precision of the position of a part of the antennamember 43 which is closer to the developing sleeve 41.

FIG. 21A is a schematic sectional view of the vicinity of the antennamember 43 illustrating the arrangement of the developing sleeve 41 andthe antenna member 43 in relation to each other in the third embodiment.The closest point A in the third embodiment is located in other placeson the antenna member 43 than the end portion B. More specifically, theclosest point A is located on the antenna member 43 between the endportion B and an end portion opposite thereto. The closest distancebetween the closest point A and the developing sleeve 41 is 5 mm, andthe distance between the closest point A and the end portion B is 3 mmin the third embodiment. The closest distance between the end portion Band the developing sleeve 41 is 5.2 mm.

The specific arrangement of the antenna member 43 is not limited to theone in the third embodiment. It is only necessary to arrange the antennamember 43 in such a manner that the closest point A on the antennamember 43 (the second electrode) where the antenna member 43 is closestto the developing sleeve 41 is located in other places than the endportion B, which is on the side of the developing sleeve 41 (the firstelectrode) (specifically, other places than the end portion). It ispreferred for the distance between the closest point A and the endportion B to be longer because then variations in the position of theend portion B affect the precision of remaining toner amount detectionless.

Configuration of Comparative Example 5

FIG. 22A is a schematic sectional view of the vicinity of the antennamember 43 illustrating the arrangement of the developing sleeve 41 andthe antenna member 43 in relation to each other in Comparative Example5. The configuration of Comparative Example 5 is substantially the sameas that of the third embodiment, except for points specifically notedbelow.

In Comparative Example 5, the antenna member 43 which is a plate-shapedmember formed from stainless steel (SUS) (SUS sheet metal) is fixed tothe developing frame 40 by sticking the antenna member 43 to thedeveloping frame 40 with double-sided adhesive tape. In the antennamember 43 of Comparative Example 5, the closest point A to thedeveloping sleeve 41 coincides with the end portion B, which is on theside of the developing sleeve 41.

Evaluation of Third Embodiment and Comparative Example 5

In the third embodiment illustrated in FIG. 21A and Comparative Example5 illustrated in FIG. 22A, a part of the antenna member 43 where the endportion B is located in FIG. 22A was reduced in size in a directionindicated by an arrow Z (toward the other end portion of the antennamember 43) compared to that in FIG. 21A, thereby changing the positionof the end portion B by 2 mm. The influence of position precision on theprecision of remaining toner amount detection was then evaluated.

FIG. 21B shows a relation between the amount of toner actually remainingin the developer container 46 and the detected capacitance in theconfiguration of the third embodiment. FIG. 22B shows a relation betweenthe amount of toner actually remaining in the developer container 46 andthe detected capacitance in the configuration of Comparative Example 5.The solid line in FIG. 21B represents a remaining toneramount-capacitance relation in the third embodiment where the antennamember 43 is arranged as illustrated in FIG. 21A. The solid line in FIG.22B represents a remaining toner amount-capacitance relation inComparative Example 5 where the antenna member 43 is arranged asillustrated in FIG. 22A. In each of FIG. 21B and FIG. 22B, the brokenline indicates a relation present between the remaining toner amount andthe capacitance when the position of the antenna member 43 is shifted by2 mm in the manner described above.

The solid lines in FIG. 21B and FIG. 22B indicate that the detectedcapacitance does not change in the zone 1 where the remaining toneramount is m1 to m2. This is because, in the zone 1, the toner surfacelevel is between H1 and H2 as described with reference to FIG. 20A. Thetoner amount in the measurement area does not change with the reductionin remaining toner amount in this zone as described above, and thedetected capacitance is therefore constant. The amount m2 in the thirdembodiment corresponds approximately to a remaining toner amount of 20%.

The solid lines in FIG. 21B and FIG. 22B indicate that the detectedcapacitance shifts linearly with respect to the remaining toner amountin the zone 2 where the remaining toner amount is m2 to 0%. This isbecause the toner amount in the measurement area decreases when thetoner surface level shifts from H3 to H4 as described with reference toFIG. 20B.

The broken lines in FIG. 21B and FIG. 22B indicate the same trend incapacitance transitions as the one indicated by the solid lines.However, the value of the detected capacitance is overall smaller in thebroken lines than in the solid lines. This is because, as can beunderstood from FIG. 21A and FIG. 22A, shifting the position of the endportion B of the antenna member 43 pushes the antenna member 43 fartherfrom the developing sleeve 41, thereby lowering the value of thecapacitance which is detected for the same remaining toner amount. Whenthe detected capacitance is low, the remaining toner amount which isobtained by referring to the data table is small.

The differential (the amount of change) ΔC between the solid line andthe broken line in the third embodiment illustrated in FIG. 21B iscompared to the differential ΔC between the solid line and the brokenline in Comparative Example 5 illustrated in FIG. 22B to reveal that thedifferential ΔC in Comparative Example 5 is larger. The differential ΔCis larger in Comparative Example 5 than in the third embodiment for thefollowing two reasons:

Reason 1: Because the closest point A where the capacitance detectionsensitivity is the highest in the antenna member 43 coincides with theend portion B, shifting the position of the end portion B by 2 mmchanges the closest distance, which affects the capacitance detectionsensitivity most. As a result, the detected capacitance value changes(drops) significantly, thereby increasing ΔC.

Reason 2: With the antenna member 43 made smaller by 2 mm in thedirection of the arrow Z of FIG. 22A, the capacitance measurement rangeis narrowed and the detected capacitance value is reduced.

On the other hand, the third embodiment differs from Comparative Example5 in the situations of Reason 1. The closest point A where thecapacitance detection sensitivity is the highest does not coincide withthe end portion B in the antenna member 43 of the third embodiment.Shifting the position of the end portion B by 2 mm therefore does notchange the closest distance, which affects the capacitance detectionsensitivity most, and the influence on the detected capacitance value isrelatively small. As a result, the differential ΔC in the thirdembodiment is that much smaller than in Comparative Example forReason 1. Because ΔC is smaller in the third embodiment, thedifferential ΔM in the amount of toner that remains upon detection ofthe capacitance C₀, which is when an image with a blank area isgenerated, is smaller in the third embodiment at ΔM1 than in ComparativeExample 5, where the differential ΔM is ΔM2.

In the third embodiment, the closest point A and the end portion B areput in different places in the antenna member 43 as described above.This prevents the precision of remaining toner amount detection fromdropping and thus ensures that the accurate remaining toner amount isindicated until the toner is used up even when the end portion B of theantenna member 43 is accidentally shifted by a positional gap ininstallation, a tolerance of respective parts, a distortion due tothermal shrinkage, and the like. The lowering of precision in developeramount detection is therefore prevented in cases where a conductiveresin sheet is used as an electrode configured to detect capacitance.Accordingly, a developer container, a developing apparatus, a processcartridge, and an image forming apparatus that have a more inexpensiveconfiguration can be provided while maintaining or improving theprecision of developer amount detection.

Fourth Embodiment

A fourth embodiment of the present invention will be described next. Inthe fourth embodiment, components whose functions and configurations arethe same as, or equivalent to, those in the first to third embodimentsare denoted by the same reference symbols, and detailed descriptionsthereof are omitted. The fourth embodiment is, in particular, amodification example of the third embodiment.

FIG. 23A is a schematic sectional view of a part of the developingapparatus 4 according to the fourth embodiment which is in the vicinityof the antenna member 43. The antenna member 43 in the fourth embodimentis arranged in the convex portion 46 e, which is formed on the bottom ofthe developer containing portion 40 a. The closest point A is arrangedin a part of the antenna member which is in the vicinity of the peak ofthe convex portion 46 e. Compared to the third embodiment where theantenna member 43 is flat, this sets a wider distance between the endportion B of the antenna member 43 (an end portion on the side of thedeveloping sleeve 41) and the developing sleeve 41 when the closestdistance to the developing sleeve 41 is the same. The influence ofvariations in the position of the end portion B of the antenna member 43is therefore even smaller than in the third embodiment.

In the fourth embodiment, the closest distance between the closest pointA and the developing sleeve 41 is 5 mm, and the distance between theclosest point A and the end portion B is 3 mm. The closest distancebetween the end portion B and the developing sleeve 41 is 6.8 mm, whichis longer than in the third embodiment.

The fourth embodiment has been evaluated in the same manner which isused in the third embodiment. FIG. 23B shows a relation between theamount of toner actually remaining in the developer container 46 and thedetected capacitance in the configuration of the fourth embodiment. Thesolid line in FIG. 23B represents a remaining toner amount-capacitancerelation in the arrangement of the antenna member 43 according to thefourth embodiment which is illustrated in FIG. 23A. The broken line inFIG. 23B represents a relation between the remaining toner amount andthe capacitance when the position of the end portion B is shifted by 2mm by reducing in size a part of the antenna member 43 of the fourthembodiment where the end portion B is located in a direction indicatedby an arrow Z of FIG. 23A (toward the other end portion of the antennamember 43).

It is understood from FIG. 23B that shifting the position of the endportion B of the antenna member 43 has made the capacitance detected inrelation to the actual remaining toner amount smaller. The differential(amount of change) ΔC between the solid line and the broken line in thefourth embodiment illustrated in FIG. 23B has been compared with thedifferential ΔC between the solid line and the broken line inComparative Example 5 illustrated in FIG. 22B to reveal that thedifferential ΔC in Comparative Example 5 is larger. The differential ΔCis larger in Comparative Example 5 than in the fourth embodiment forReason 1 and Reason 2 given above and for one more reason given below.

Reason 3: When the closest distance is the same, arranging the closestpoint A in the convex portion 46 e sets a wider distance between the endportion B and the developing sleeve 41 than when the antenna member 43is flat as in Comparative Example 5. This reduces the influence of apositional gap of the end portion B on the detected capacitance valueeven more.

The differential ΔC in the fourth embodiment is thus smaller than inComparative Example 5. As a result, the differential ΔM in the amount oftoner that remains upon detection of the capacitance C₀, which is whenan image with a blank area is generated, is smaller in the fourthembodiment at ΔM3 than in Comparative Example 5, where the differentialΔM is ΔM2.

The differential ΔC in the fourth embodiment is smaller than ΔC in thethird embodiment, and the differential ΔM3 in the fourth embodiment issmaller than ΔM1 in the third embodiment. This, too, is presumablybecause of Reason 3.

According to the fourth embodiment, the same effects as those of thethird embodiment are obtained, and arranging the closest point A in theconvex portion 46 e provides an additional effect in that the loweringof the precision in remaining toner amount detection is prevented evenbetter.

Fifth Embodiment

Another embodiment of the present invention will be described next. Inthe fifth embodiment, components whose functions and configurations arethe same as, or equivalent to, those in the first to fourth embodimentsare denoted by the same reference symbols, and detailed descriptionsthereof are omitted. The fifth embodiment is, in particular, anothermodification example of the third embodiment.

In the third embodiment and the fourth embodiment, the remaining toneramount that can be detected is 20% to 0%. This is because the third andfourth embodiments are configured so that the toner amount in themeasurement area does not change until the remaining toner amount dropsto 20%. The remaining toner amount which is around 0% can be detectedwith high precision by placing the antenna member close to thedeveloping sleeve 41. However, the remaining toner amount measurementarea may become smaller in this case. In order to start remaining toneramount detection from an earlier stage where the remaining toner amountis larger while maintaining the precision in the detection of theremaining toner amount around 0%, expanding the measurement area by theantenna member 43 is desired.

A method of expanding the remaining toner amount measurement area thathas been used in the past is to stick a plurality of (two, for example)antenna members 43 which are formed from SUS sheet metal or the like tothe developer container 46 with double-sided adhesive tape or the like,as in Comparative Example 6 (FIG. 25A) which will be described later.Each antenna member 43 is connected separately to a capacitancedetecting circuit in this case. In this configuration, however, thedistance tolerance described in the third embodiment is brought into theequation by each antenna member 43 stuck to the developer container 46,and causes the remaining toner amount detection result to vary. Stickinga plurality of (two, for example) antenna members 43 also requires moresteps of manufacturing the developer container 46 and higher cost thanin, for example, Comparative Example 5.

FIG. 24A is a schematic sectional view of a part of the developingapparatus 4 according to the fifth embodiment which is in the vicinityof the antenna member 43. The antenna member 43 in the fifth embodimentis sequentially arranged in the convex portion 46 e to the concaveportion 46 f, which is formed on the bottom of the developer containingportion 40 a. This gives the antenna member 43 two surfaces, ameasurement area 1 and a measurement area 2, as measurement areas whichare opposed to the developing sleeve 41 and in which the capacitance canbe measured. The antenna member 43 also has one surface as anon-measurement area which is located between the convex portion 46 eand the concave portion 46 f and behind the convex portion 46 e withrespect to the developing sleeve 41 and in which the capacitance cannotbe measured. The antenna member 43 in the fifth embodiment thus has atleast one convex portion 46 e protruding toward the developing sleeve 41(toward the first electrode), and the closest point A is located in theconvex portion 46 e. The antenna member 43 in the fifth embodiment alsohas at least one concave portion 46 f which is opposite to thedeveloping sleeve 41 with respect to the convex portion 46 e. The singleantenna member 43 thus forms a plurality of surfaces which are opposedto the developing sleeve 41.

Specifically, a broken line R1 in FIG. 24A is a tangent line of thedeveloping sleeve 41 that runs through a point where a boundary line R4of an area behind the convex portion 46 e with respect to the developingsleeve 41 is in contact with the antenna member 43 on the side of thedeveloping sleeve 41 (in the vicinity of the peak of the convex portion46 e). A broken line R2 is a tangent line of the developing sleeve 41that runs through the end portion B of the antenna member 43 on the sideof the developing sleeve 41. An area surrounded by the broken line 1,the broken line 2, the surface of the developing sleeve 41, and one ofthe surfaces of the antenna member 43 is the remaining toner amountmeasurement area 1. A broken line R3 in FIG. 24A is a tangent line ofthe developing sleeve 41 that runs through an end portion of the antennamember 43 which is on the side opposite to the developing sleeve 41. Abroken line R4 is the boundary line of the area behind the convexportion 46 e with respect to the developing sleeve 41. An areasurrounded by the broken line R3, the broken line R4, the surface of thedeveloping sleeve 41, and one of the surfaces of the antenna member 43is the remaining toner amount measurement area 2. An area in FIG. 24Awhich is enclosed by a surface of the antenna member 43 and the brokenline R4 is the non-measurement area where the remaining toner amount isnot measured.

FIG. 24B shows a relation between the remaining toner amount and thecapacitance which is obtained in advance in the configuration of thefifth embodiment in the manner described above. The axis of abscissaindicates the remaining toner amount and the axis of ordinate indicatesthe detected capacitance. The capacitance which is detected when theremaining toner amount is 0% and an image with a blank area is generatedis represented by C₀.

In FIG. 24B, the capacitance is constant irrespective of the remainingtoner amount in the zone 1 where the remaining toner amount is m1 to m2.The toner surface level in this zone is at H5 in FIG. 24A. The tonersurface level is above H5 when the process cartridge 120 is new, andgradually shifts to H5 as the toner is consumed by forming images. Untilthe toner surface level reaches H5, each measurement area is filled withthe toner and the capacitance is therefore constant irrespective of theremaining toner amount. This zone is where the remaining toner amount is100% to 50% in the fifth embodiment.

Next, the capacitance decreases with the reduction of the remainingtoner amount in a zone 2 of FIG. 24B where the remaining toner amount ism2 to m3. The toner surface level in this zone is between H5 and H6 inFIG. 24A. When the toner surface level is between H5 and H6, the toneramount changes in the measurement area 2, and changes in capacitance inthe zone 2 are therefore dominated by results of detection in themeasurement area 2. This zone is where the remaining toner amount is 50%to 30% in the fifth embodiment.

Next, in FIG. 24B, the capacitance is constant again irrespective of theremaining toner amount in the zone 3 where the remaining toner amount ism3 to m4. The toner surface level in this zone is, for example, at H7 inFIG. 24A. When the toner is in the non-measurement area, the toneramount in the area cannot be measured and the capacitance is thereforeconstant irrespective of the remaining toner amount. This zone is wherethe remaining toner amount is 30% to 20% in the fifth embodiment.

When the toner surface level is between H5 and H7, the vicinity of thedeveloping sleeve 41 is substantially filled with the toner fed from theagitating member 45, and the result of detection in the measurement area1 does not change much.

Next, in a zone 4 of FIG. 24B where the remaining toner amount is m4 to0%, the remaining toner amount and the capacitance have a linearrelation again. The toner surface level in this zone changes in themanner described in the third embodiment with reference to FIG. 20B.Specifically, the toner surface level changes from H7 to H8 of FIG. 24A.While the toner surface level changes from H7 to H8, the toner amount inthe measurement area 1 changes, and changes in capacitance in the zone 4are therefore dominated by results of detection in the measurement area1. This zone is where the remaining toner amount is 20% to 0% in thefifth embodiment.

Configuration of Comparative Example 6

FIG. 25A is a schematic sectional view of a part of the developingapparatus 4 according to Comparative Example 6 which is in the vicinityof the antenna member 43. The configuration of Comparative Example 6 issubstantially the same as that of the fifth embodiment, except forpoints specifically noted below. In Comparative Example 6, two antennamembers are provided which are a first antenna member 43 a and a secondantenna member 43 b, and which are made from SUS sheet metal. The firstantenna member 43 a and the second antenna member 43 b are each arrangedso as to face the developing sleeve 41. In order to detect the remainingtoner amount in a wider range than in Comparative Example 5 describedabove, the first antenna member 43 a is arranged in the vicinity of thedeveloping sleeve 41 and the second antenna member 43 b is arranged at adistance from the developing sleeve 41. In each of the first antennamember 43 a and the second antenna member 43 b, the closest point A tothe developing sleeve 41 and the end portion B on the side of thedeveloping sleeve 41 coincide with each other. The first antenna member43 a and the second antenna member 43 b are connected to the sameelectric potential and are connected to an earth via the capacitancedetecting circuit 132.

Evaluation of Fifth Embodiment and Comparative Example 6

The fifth embodiment and Comparative Example 6 were evaluated in thesame manner as in the third embodiment. In the fifth embodimentillustrated in FIG. 24A and Comparative Example 6 illustrated in FIG.25A, the end portion B of the antenna member 43 on the side of thedeveloping sleeve 41 was reduced in size in a direction indicated by anarrow Z of the drawing (toward the other end portion of the antennamember 43), thereby changing the position of the end portion B by 2 mm.The influence of position precision on the precision of remaining toneramount detection was then evaluated. In Comparative Example 6, theposition of the end portion B on the side of the developing sleeve 41was changed by 2 mm in the manner described above in each of the firstantenna member 43 a and the second antenna member 43 b.

FIG. 24C shows a relation between the amount of toner actually remainingin the developer container 46 and the detected capacitance in theconfiguration of the fifth embodiment. FIG. 25B shows a relation betweenthe amount of toner actually remaining in the developer container 46 andthe detected capacitance in the configuration of Comparative Example 6.The solid line in FIG. 24C represents a remaining toneramount-capacitance relation in the fifth embodiment where the antennamember 43 is arranged as illustrated in FIG. 24A. The solid line in FIG.25B represents a remaining toner amount-capacitance relation inComparative Example 6 where the antenna member 43 is arranged asillustrated in FIG. 25A. In each of FIG. 24C and FIG. 25B, the brokenline indicates a relation between the remaining toner amount and thecapacitance when the position of the antenna member 43 on the endportion B side is shifted by 2 mm in the manner described above.

It is understood from FIG. 24C and FIG. 25B that shifting the positionof the end portion B of the antenna member 43 made the capacitancedetected in relation to the actual remaining toner amount smaller. Thedifferential (amount of change) ΔC between the solid line and the brokenline in the fifth embodiment shown in FIG. 24C is compared to thedifferential ΔC between the solid line and the broken line inComparative Example 6 shown in FIG. 25B to reveal that the differentialΔC in Comparative Example 6 is larger. The differential ΔC is larger inComparative Example 6 than in the fifth embodiment for Reason 1, Reason2, and Reason 3 given above.

The differential ΔC in the fifth embodiment is thus smaller than inComparative Example 6. As a result, the differential ΔM in the amount oftoner that remains upon detection of the capacitance C₀, which is whenan image with a blank area is generated, is smaller in the fifthembodiment at ΔM4 than in Comparative Example 6, where the differentialΔM is ΔM5.

According to the fifth embodiment, the same effects as those of thethird embodiment and the fourth embodiment are obtained. In addition,the remaining toner amount can be indicated sequentially from an earlystage where the remaining toner amount is large by increasing the numberof antenna members or the like, without furthering the lowering of theprecision in remaining toner amount detection.

According to the embodiments disclosed herein, the developer containerof which the developer amount is detected by the capacitance detectionmethod is manufactured easily. The developer container, the developingapparatus, and the process cartridge according to the embodimentsdisclosed herein can improve detection precision when the developeramount is detected by the capacitance detection method with the use of aconductive resin member as an electrode.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

What is claimed is:
 1. A method of manufacturing a developer container,including a frame configured to define a developer containing portion,of a developing device having an electrode which is used for outputtingan output reflecting capacitance according to a developer amount storedin the developer containing portion and is arranged on an inner surfaceof the frame of the developer containing portion, the method comprising:holding a conductive resin sheet, serving as the electrode, to positionthe conductive resin sheet on a mold configured to mold the frame, theholding including: bringing a surface of the conductive resin sheet intocontact with a surface of the mold, the mold forming a surface of theframe on a side of the containing portion for a developer; and holding afirst area of the conductive resin sheet at a holding area of the moldby a holding unit; injecting a resin to be formed into the frame, from agate provided in the mold on which the conductive resin sheet is held;curing the resin to form the frame to which the conductive resin sheetis fixed, wherein the conductive resin sheet has one end and an otherend with respect to a lateral direction of the conductive resin sheet,the lateral direction intersecting a longitudinal direction of theconductive resin sheet, and wherein the other end is positioned fartheraway from the first area than the one end, and the other end ispositioned downstream of the one end in a direction in which the resininjected from the gate is spread out.
 2. The method according to claim1, wherein an injection direction of the resin in the gate is athickness direction of the frame.
 3. The method according to claim 1,wherein a thickness of the conductive resin sheet is 0.05 mm to 0.3 mm.4. The method according to claim 1, wherein a part of the conductiveresin sheet extending from the first area to the other end excluding thefirst area corresponds to a second area, and the conductive resin sheetin the second area is not held by the holding unit through the holdingarea.
 5. A method of manufacturing a developer container, including aframe configured to define a developer containing portion, of adeveloping device having an electrode which is used for outputting anoutput reflecting capacitance according to a developer amount stored inthe developer containing portion and is arranged on an inner surface ofthe frame of the developer containing portion, the method comprising:holding a conductive resin sheet, serving as the electrode, to positionthe conductive resin sheet on a mold configured to mold the frame, theholding including: bringing a surface of the conductive resin sheet intocontact with a surface of the mold, the mold forming a surface of theframe on a side of the containing portion for a developer; and holdingthe conductive resin sheet at a holding area of the mold by a holdingunit; injecting a resin to be formed into the frame, from a gateprovided in the mold on which the conductive resin sheet is held; curingthe resin to form the frame to which the conductive resin sheet isfixed, wherein the holding unit holds an area on one end side of theconductive resin sheet in a lateral direction of the conductive resinsheet at the holding area, the lateral direction intersecting alongitudinal direction of the conductive resin sheet, and wherein another end side opposed to the one end side in the lateral direction isnot held at the holding area and is farther away from the gate than theone end side in the lateral direction.
 6. The method according to claim5, wherein an injection direction of the resin in the gate is athickness direction of the frame.
 7. The method according to claim 5,wherein a thickness of the conductive resin sheet is 0.05 mm to 0.3 mm.8. The method according to claim 5, wherein a part of the conductiveresin sheet extending from a first area to the other end side excludingthe first area of the conductive resin sheet held at the holding areacorresponds to a second area, and the conductive resin sheet in thesecond area is not held by the holding unit through the holding area. 9.A method of manufacturing a developer container, including a frameconfigured to define a developer containing portion, of a developingdevice having an electrode which is used for outputting an outputreflecting capacitance according to a developer amount stored in thedeveloper containing portion and is arranged on an inner surface of theframe of the developer containing portion, the method comprising:holding a conductive resin sheet, serving as the electrode, to positionthe conductive resin sheet on a mold configured to mold the frame, theholding including: bringing a surface of the conductive resin sheet intocontact with a surface of the mold, the mold forming a surface of theframe on a side of the containing portion for a developer; and holding afirst area of the conductive resin sheet at a holding area of the moldby a holding unit; injecting a resin to be formed into the frame, from agate provided in the mold on which the conductive resin sheet is held;curing the resin to form the frame to which the conductive resin sheetis fixed, wherein the conductive resin sheet has one end and an otherend with respect to a lateral direction of the conductive resin sheet,the lateral direction intersecting a longitudinal direction of theconductive resin sheet, and wherein the other end is positioned fartheraway from the first area than the one end, and the other end ispositioned farther away from the gate than the first area.
 10. Themethod according to claim 9, wherein an injection direction of the resinin the gate is a thickness direction of the frame.
 11. The methodaccording to claim 9, wherein a thickness of the conductive resin sheetis 0.05 mm to 0.3 mm.
 12. The method according to claim 9, wherein apart of the conductive resin sheet extending from the first area to theother end excluding the first area corresponds to a second area, and theconductive resin sheet in the second area is not held by the holdingunit through the holding area.
 13. The method according to claim 1,wherein the conductive resin sheet has a surface on a side of the frame,the surface being constituted by a material which has compatibility withor adhesiveness to the resin to be formed into the frame.
 14. The methodaccording to claim 1, wherein the holding includes holding theconductive resin sheet by air suction through a hole provided in themold.
 15. The method according to claim 1, wherein a surface of the moldon which the conductive resin sheet is held comprises a curved surface.16. The method according to claim 1, wherein the injecting includesinjecting the resin in a direction intersecting the longitudinaldirection of the conductive resin sheet.
 17. The method according toclaim 5, wherein the conductive resin sheet has a surface on a side ofthe frame, the surface being constituted by a material which hascompatibility with or adhesiveness to the resin to be formed into theframe.
 18. The method according to claim 5, wherein the holding includesholding the conductive resin sheet by air suction through a holeprovided in the mold.
 19. The method according to claim 5, wherein asurface of the mold on which the conductive resin sheet is heldcomprises a curved surface.
 20. The method according to claim 5, whereinthe injecting includes injecting the resin in a direction intersectingthe longitudinal direction of the conductive resin sheet.
 21. The methodaccording to claim 9, wherein the conductive resin sheet has a surfaceon a side of the frame, the surface being constituted by a materialwhich has compatibility with or adhesiveness to the resin to be formedinto the frame.
 22. The method according to claim 9, wherein the holdingincludes holding the conductive resin sheet by air suction through ahole provided in the mold.
 23. The method according to claim 9, whereina surface of the mold on which the conductive resin sheet is heldcomprises a curved surface.
 24. The method according to claim 9, whereinthe injecting includes injecting the resin in a direction intersectingthe longitudinal direction of the conductive resin sheet.